School teaching is regarded as a stressful occupation. The present study aimed to compare the likelihood of having minor psychiatric disorders (MPD) among school teachers with that among civil servants, and to investigate what factors were specifically associated with MPD in teachers. We conducted a questionnaire-based survey of 403 teachers employed at state schools and 611 civil servants as a comparison group in a medium-sized city in Japan. The response rate was 59.6% for teachers and 62.0% for civil servants. Mental health was assessed using the 28-item General Health Questionnaire (GHQ-28), according to which those with a score of six or higher were considered to have MPD. Logistic regression analysis was used to identify the factors associated with MPD. Although the proportion of subjects with MPD among teachers was greater than that among civil servants, the difference in the proportion was not statistically significant in the multiple logistic regression analysis adjusted for potential confounders. In a separate analysis of the teachers, reduced job satisfaction and shorter time spent of leisure were significantly associated with an increased likelihood of having MPD. In the group of civil servants, longer working hours, reduced life satisfaction, a history of sick leave, and physical illness were associated with an increased likelihood of having MPD. When this analysis was conducted separately for male and female teachers, job dissatisfaction alone was associated with MPD only in female teachers. Poor mental health of Japanese school teachers, female teachers in particular, was found to be associated with job dissatisfaction.