Investigation by Labour Standards Inspection Office in Japan

In Japan, the Labour Standards Inspection Office (労働基準監督署 / Rōdō Kijun Kantokusho) is responsible for enforcing labour-standards legislation at workplaces. Labour Standards Inspectors can enter workplaces, inspect records and equipment, question employers and workers, and investigate suspected violations. In serious cases, inspectors can act as special judicial police officers and refer criminal cases to the Public Prosecutor's Office.

1. Meaning of Investigation

An investigation by a Labour Standards Inspection Office is an official examination of whether an employer is complying with laws such as:

• Labour Standards Act;
• Industrial Safety and Health Act;
• Minimum Wages Act;
• Industrial Accident Compensation Insurance Act-related provisions;
• Pneumoconiosis Act; and
• other labour-standard legislation administered by labour inspectors.

The investigation may arise from a worker's complaint or information, a planned inspection, or a serious workplace accident. The Ministry of Health, Labour and Welfare states that inspections can also be conducted following information supplied by workers or others.

2. Main Objectives

The investigation generally aims to determine whether:

1. statutory working hours are being observed;
2. overtime is properly managed and paid;
3. wages are paid correctly and on time;
4. minimum-wage requirements are satisfied;
5. dismissal-related statutory requirements are followed where applicable;
6. workplace safety requirements are being followed;
7. occupational-health measures are adequate;
8. accidents have been properly reported and investigated;
9. required records have been maintained; and
10. dangerous working conditions are being corrected.

The objective is therefore both compliance enforcement and prevention of harm.

3. How an Investigation Can Begin

A. Regular or planned inspection

Labour Standards Inspectors may conduct inspections as part of administrative enforcement activities.

B. Worker complaint or report

A worker can provide information concerning suspected violations.

Examples include:

• unpaid overtime;
• unpaid wages;
• excessive working hours;
• unsafe machinery;
• failure to provide legally required safety measures;
• failure to maintain required records.

The Ministry states that information received concerning suspected violations may be used when selecting workplaces for on-site investigation.

C. Serious workplace accident

When a serious industrial accident, fire or explosion occurs, an accident-site inspection may be conducted to establish the cause and prevent recurrence.

D. Information obtained by authorities

Authorities may also initiate investigations based on information suggesting non-compliance.

4. Entry into the Workplace

A Labour Standards Inspector has statutory authority to enter the workplace for inspection.

Under Article 101 of the Labour Standards Act, an inspector may:

• enter the workplace and related premises;
• require submission of books and documents; and
• question the employer or workers. 

The Ministry explains that inspections may be conducted without advance notice, allowing inspectors to observe actual working conditions rather than only conditions prepared for an inspection.

5. Documents Examined

During an investigation, inspectors may examine documents relevant to compliance, including:

Employment records

• employment contracts;
• work rules;
• personnel records;
• attendance records.

Working-time records

• time cards;
• electronic attendance data;
• overtime records;
• 36 Agreements;
• shift schedules.

Payroll records

• wage ledgers;
• payslips;
• overtime calculations;
• deductions;
• payment records.

Safety and health records

• risk assessments;
• safety training records;
• equipment inspection records;
• accident reports;
• health-examination records;
• workplace-environment measurements.

The purpose is to compare documented information with actual working conditions.

6. Interviews and Questioning

Inspectors can question:

• company directors;
• managers;
• supervisors;
• HR personnel;
• safety officers; and
• workers.

This is important because written records may not accurately reflect actual working practices.

For example, a company may record that an employee worked eight hours per day, while interviews and computer-access records may indicate substantial additional work.

7. Physical Inspection

Where health and safety are involved, inspectors may examine:

• machinery;
• production equipment;
• protective guards;
• ventilation;
• emergency exits;
• protective equipment;
• hazardous substances;
• workplace layout;
• electrical installations; and
• other dangerous conditions.

Where there is an imminent danger, administrative measures can include an order stopping the use of dangerous machinery or equipment.

8. Investigation of Working Hours

Working hours are one of the important areas of labour inspection.

Inspectors may compare:

attendance records + payroll records + overtime records + actual working practices.

They may investigate:

• unpaid overtime;
• excessive overtime;
• incorrect recording of working hours;
• work performed before or after recorded hours;
• inadequate breaks;
• violations involving statutory working hours; and
• improper operation of overtime arrangements.

The Dentsu case is particularly significant in this context.

9. Dentsu Case — Supreme Court, 24 March 2000

Case Numbers: 1998 (O) Nos. 217 and 218
Minshu Vol. 54, No. 3, p. 1155

An employee of Dentsu worked extremely long hours over an extended period and subsequently developed depression and died by suicide.

The Supreme Court recognised the employer's duty to take appropriate care of an employee's physical and mental health in relation to excessive fatigue and psychological stress caused by work. The judgment also described a workplace where long overtime was common and overtime reporting did not necessarily reflect the actual circumstances.

Importance for Labour Standards Inspection:
An investigation should not automatically accept attendance records at face value. Inspectors may need to examine the actual working pattern, overtime practices, instructions from managers and the relationship between recorded and actual hours.

10. Investigation of Wages

Inspectors may examine whether employees have received:

• basic wages;
• overtime payments;
• statutory premium payments;
• holiday-related payments;
• minimum wages; and
• other amounts protected by labour legislation.

If a violation is identified, the employer may be instructed to correct it.

The Japanese labour administration describes correction of violations as a central part of labour inspection.

11. Investigation of Health and Safety

The Labour Standards Inspection Office also investigates compliance with occupational safety and health requirements.

Areas include:

• machinery safety;
• dangerous work;
• hazardous substances;
• ventilation;
• protective equipment;
• safety education;
• health examinations;
• workplace environment;
• accident prevention; and
• occupational diseases.

12. Asbestos Case — Supreme Court, 9 October 2014

Case Number: 2014 (Ju) No. 771

This case concerned asbestos-related diseases and the State's failure to exercise regulatory authority under the former Labour Standards Act and Industrial Safety and Health Act.

The Supreme Court considered the history of asbestos regulation, including ventilation and measures for preventing exposure to asbestos dust. The Court emphasised that occupational-safety regulation must respond appropriately to established medical and technical knowledge.

Importance for investigation:
Where hazardous substances are involved, inspectors need to investigate not merely whether an employer has a written policy, but whether actual exposure-prevention measures are effective.

13. Asbestos Construction Workers Case — Supreme Court, 17 May 2021

Case Number: 2018 (Ju) No. 1447

The Supreme Court considered asbestos exposure involving construction workers.

The Court examined issues including:

• asbestos dust;
• construction-site conditions;
• ventilation;
• respiratory protection;
• warnings;
• information concerning hazardous materials; and
• regulatory supervision. 

Importance for investigation:
An investigation of a hazardous workplace should consider the actual conditions under which workers perform their jobs, including whether warnings and protective measures are actually functioning.

14. Investigation Following Industrial Accidents

When a serious accident occurs, an investigation may focus on:

1. what happened;
2. where it happened;
3. which workers were involved;
4. what equipment was being used;
5. whether safety procedures existed;
6. whether those procedures were followed;
7. whether management knew about the danger;
8. whether previous accidents or warnings existed; and
9. what measures are necessary to prevent recurrence.

Japanese labour administration specifically describes accident-site inspection as a means of investigating the cause and preventing recurrence.

15. Mitsubishi Motors Case — Supreme Court, 8 February 2012

Case Number: 2009 (A) No. 359

The Supreme Court considered an accident involving a Mitsubishi Motors truck wheel hub and the responsibilities of personnel dealing with safety-related information.

The case concerned the response to known safety problems and whether appropriate measures should have been taken.

Importance for labour investigations:
The case illustrates a broader safety principle: where an organisation receives information indicating a serious safety risk, investigators may examine whether responsible personnel recognised the risk and took appropriate action.

This principle is particularly relevant when investigating whether a workplace accident was an isolated event or the result of a known and insufficiently addressed hazard.

16. Mental-Health Investigation

Modern labour investigations can also involve psychological health.

Inspectors may examine:

• excessive overtime;
• workload;
• consecutive working days;
• managerial instructions;
• stress information;
• complaints;
• requests for workload reduction; and
• measures taken by management.

2025 Police Inspector Case — Supreme Court, 7 March 2025

Case Number: 2023 (Ju) No. 927

The Supreme Court considered a case involving a prefectural police inspector who committed suicide following a period of very heavy work.

The Court noted that immediately before the suicide the inspector worked more than 112 hours of overtime in one month, worked two periods of 14 consecutive days with only one day off between them, and had received the worst rating in a workplace stress test. The Court held that the superiors had a duty of care to protect the inspector's physical and mental health and had failed to take concrete measures to reduce the burden.

Importance for inspection:
An investigation into excessive work should examine the complete picture rather than relying solely on one document or one month's payroll record.

17. Investigation of Hazardous Substances

In hazardous-substance cases, inspectors may examine:

• what substance was used;
• quantity and concentration;
• exposure levels;
• ventilation;
• protective equipment;
• warning labels;
• training;
• worker instructions;
• maintenance records; and
• previous inspection findings.

The asbestos cases show why regulatory compliance must be connected with actual exposure risks.

18. What Happens When a Violation Is Found?

The response depends on the seriousness and circumstances of the violation.

Administrative correction

For many violations, inspectors may instruct the employer to correct the situation.

Examples:

• pay unpaid wages;
• correct working-time records;
• improve safety measures;
• repair dangerous equipment;
• provide required training.

Improvement of dangerous conditions

Where dangerous machinery or equipment presents an urgent risk, an inspector may take or initiate measures requiring its use to be stopped.

Criminal investigation

Serious or malicious violations can be investigated as criminal matters.

The Labour Standards Act gives inspectors judicial-police functions for offences under the Act. Article 102 provides that inspectors perform the functions of judicial police officers concerning crimes involving violations of the Act.

The Ministry states that serious and gross violations can be investigated as criminal cases and referred to the Public Prosecutor's Office.

19. Refusal to Cooperate

Employers and others cannot simply obstruct a lawful inspection.

The Ministry explains that refusal, obstruction, avoidance of questioning, failure to submit required documents, or submission of false records can result in punishment under the Labour Standards Act.

Therefore, maintaining accurate records is important not only for ordinary compliance but also during an inspection.

20. Six Important Case Laws and Their Relevance

The Supreme Court's 2021 asbestos judgment itself refers to earlier asbestos decisions, including the 27 April 2004 and 15 October 2004 judgments, in developing the relevant legal reasoning.

21. Difference Between Internal Audit and Labour Standards Inspection

22. Practical Example

Suppose a Japanese factory reports that an employee suffered a serious machinery injury.

The Labour Standards Inspection Office may:

Step 1: Visit the factory.

Step 2: Inspect the machinery.

Step 3: Examine the safety guard and emergency-stop mechanism.

Step 4: Interview the injured worker and colleagues.

Step 5: Examine safety-training records.

Step 6: Examine maintenance and inspection records.

Step 7: Determine whether the machine complied with applicable safety requirements.

Step 8: Determine whether management knew about previous defects.

Step 9: Identify the immediate and underlying causes.

Step 10: Require appropriate corrective measures and, where legally warranted, take further enforcement action.

This approach reflects the Japanese labour administration's dual emphasis on compliance and prevention of recurrence.

Conclusion

Investigation by the Labour Standards Inspection Office is an important enforcement mechanism in Japan's employment-law system. Inspectors have authority to enter workplaces, examine documents, question employers and workers, investigate accidents and inspect safety conditions. Where violations are found, the response may range from corrective administrative guidance to stronger enforcement, including criminal referral in serious cases.

The Dentsu, asbestos, Mitsubishi Motors and 2025 police-inspector cases demonstrate why an investigation must look beyond formal policies and examine the actual working conditions, employer knowledge, available safety information and measures taken to prevent harm.