The purpose of this paper is to clarify the actual situation of club activities in junior high school and teachers' awareness of them by focusing on school size. Recently in Japan, there are a lot of discussions about work-type reforms regarding the way teachers work in public and academic levels because many surveys showed that the working hours of teachers in japan have been too long. And club activities have been pointed out as the cause of overworking, however, there have been few studies of the working hours of teachers and actual situations of club activities by focusing on school size. Therefore, in this paper, we examine the actual situation of club activities and how the teachers think about them by focusing the class size which means the number of students. The results of this paper are as follows. First, there are differences regarding working hours and hours of club activities depending on school size, which suggests that teachers who work at larger schools work much longer. Secondly, the larger schools offer more types of club activities yet less rest days from club activities during holidays. And the ratio of teachers who teach club activities is equal but teachers who work at smaller school coach alone. Finally, teachers who work at larger schools tend to prefer to coach club activities much longer than teachers who work at smaller schools. Regarding this, we suggested that teachers who work at larger schools have more chances to coach club activities for which they have had experience through their own junior high school years; also, they are able to coach prefered activities as there is a larger number of activities to choose from in a larger school. Based on the above, this paper suggests that the school size and the number of club activities play an important role in securing a workload more acceptable for teachers and their duties with club activities.