The purpose of this study was to test the moderating effect of school sports club participation in relation between happiness in school and deviant behavior. The participants were 278 middle school students. All the students administered three instruments, happiness in school scale, school sports club participation scale, deviant behavior scale. The results were as follows: First, there are significant relationship among happiness in school, sports club participation and deviant behavior. Second, it was proved that the significantly different results at happiness in school and deviant behavior scores between higher group and lower group of school sports club participation. Third, moderated effect of school sports club participation had been shown in the relationship between happiness in school and deviant behavior. The implications of this study were investigated variables regarding deviant behavior to help middle school students. Based on the finding results, how to increase school sports club participation and happiness in school and reduce deviant behavior were suggested.