In Japan, a study on mental health in workplace has expanded from tertiary to secondary and primary preventions of mental health disorders among employees. Recent movements suggest a trend of bringing numerous topics outside the industrial health, including those with perspectives from categories generally known as primordial prevention, such as enhancement of working life quality or improvement of work environment.First, according to the aforementioned trends, the present paper made an effort to organize the terms and concepts related to mental health disorders, which included the foundation for research and practice in this area as well as the outcomes of discussions on the tertiary and secondary preventions.Second, the primary models of work-related stress, along its impact on mental health, and the scales for assessing workers' mental health issues were discussed, which have been used in numerous studies since the 1990s. The introduction of those models and scales contributed immensely to the expansion of this field's research areas. However, a number of significant factors, most of which have social or cultural implications, can influence the connection between stress at workplace and health problems. Therefore, conducting large-scale study or systematic reviews targeting domestic cases exclusively is necessary to obtain evidence for establishing highly versatile measures against mental health problems in Japan.Third, in this regard, several noteworthy large-scale research projects in Japan are highlighted as a hope for encouraging such studies in this field. However, the occupational health practitioners' effort to understand the actual workplace situations where they attend to and to put the understanding into practice has been and will remain an indispensable attribute for them in the future.