This review paper describes current situations and challenges of occupational mental health in Japan, state-of-art of occupational mental health activities, and its future directions. The recent challenges include increasing incidence of depressive disorders, more involvement of business perspectives, widening social inequality in a workplace, harassment and mobbing at work, mental health problems related to overwork, and lower implementation of occupational mental health activities in medium and small-sized enterprises. The current activities for occupational mental health, based on the Japan Ministry of Health, Labour, and Welfare "the Guideline for Promotion and Maintenance of Mental Health among Workers", consists of four major activities, i.e., education/training and information dissemination, work environment improvement, consultation for workers with mental health problems, and support for return-to-work of workers with mental health problems. These activities are very basic ones; However, they may be not enough effective for the recent challenges. Future activities for occupational mental health may include the evaluation and improvement of psychosocial stress in a company organization, the primary prevention of depressive disorders, and a service provided to support return-to-work of workers with mental health problems in medium and small-sized enterprises.