We explored the factors that affect working hours and excessive workload for managerial staff by using the microdata accumulated by the Japan Institute for Labour Policy and Training (JILPT). On average, division managers and depart-日本労働研究雑誌 115 ment managers work longer than rank-and-file employees. Even if the influence of various attributes is set constant, managerial staff works longer than rank-and-file employees to some extent. We also examined the differences among managerial staff. To discuss the issues with ‶managers" exempted from ‶supervision of working hours," we examined how ‶discretionary decisions on clocking-in and clocking-out time" affect excessive workload and found that the former does not affect the latter at all. Many managerial staff works long hours in their own way whether or not they decide the clocking-out time at their own discretion. Accordingly, it is considered meaningless in the present setting to exempt an employee from ‶supervision of working hours" merely because he is in a managerial position in the sense that managerial staff decides how long they work at their own discretion. We learned, however, that personnel affairs like recruitment and assignment affect excessive workload. This may be the problem which is specific to managerial staff and is irrelevant to rank-and-file employees.