In order to clarify the relationships between lifestyle behaviors and mental health status in Japanese workers, the 28-item General Health Questionnaire (GHQ-28) and Zung's Self-rating Depression Scale (SDS) were administered to 254 male factory workers; further, eight of their personal health practices were surveyed using the Health Practice Index (HPI). Few studies have used the GHQ-28 and SDS simultaneously; moreover, to date, no study has included the lifestyle factors in these scales. We used these tools for the concurrent assessment of mental health status and classified the subjects into high-risk and low-risk groups. The GHQ-28 and SDS scores correlated negatively with the HPI scores. In the older age group, these scores decreased significantly corresponding to an increase in the total number of favorable lifestyle practices followed. Significant relationships were observed between the GHQ-28 subscales and the HPI. Multiple logistic regression analysis revealed that four of the eight health practices surveyed were significantly related to the mental health status in all subjects. Thus, good health practices appear to be closely associated with good mental health status. However, to establish our results, larger study populations are required for further studies in various occupational fields.