Past research indicated that the long working hours might lead to highly depression risk, and the criterion was 40 hours. The purpose of this study is to explore if this phenomenon also remains in high school, junior high school, and elementary school teacher groups. Hence, how the function of subjective well-being mediating the relationship between working hours and depression was working is investigated. There are 984 teachers randomly selected from the north, the central, and the south of Taiwan. All of the participants have to complete two questionnaires, i.e., Subjective Well-Being Scale and Taiwan Depression Scale, to measure the subjective well-being and depression. The results show that teachers with longer working hours would have higher risk in depression. Second, working hours were different among three levels of teachers. Third, subjective well-being might be the mediator between working hours and depression for high school teachers. Finally, some suggestions for practical application and future research are proposed.