The purpose of this article is to analyze the effect of bukatsudo (Japanese extracurricular activities) on academic achievement, educational aspiration and on high school life. In Japan, bukatsudo is very important activity for high school students in two aspects; (1) school life and (2) curriculum. In spite of such importance, the effect has not been examined yet. This analysis examines the effect of bukatsudo from three points of views; (1) the relation between participation in bukatsudo and, academic achievement and educational aspiration, (2) the relation between participation in bukatsudo and high school student culture, (3) the process of the effects of bukatsudo on academic achievement. Respondents are 992 students in 4 high schools (one of higher, one of middle, two of lower academic level). The results may be summarized as follows: 1 participation in bukatsudo has positive effect on academic achievement. 2)The effect on academic achievement is not direct, but indirect. Because participation in bukatsudo promotes students' adaptation to school, their academic achievement increases. These effects are strongest in high school of lower academic level. 3) The effect is different given the hierarchical status of the schools. The reason for this difference may be refered to as follows. In high schools of higher academic level, students' value is linked with academic achievement. On the contrary, in high schools of lower academic level, bukatsudo is important activities in students' social world.