The purpose of this study was to explore the determinants of subjective happiness among Korean adolescents and to supply basic data for enhancing to subjective happiness among Korean adolescents. This study used the 2014 Korean Youth Health Risk Behavior On-lin Survey data. It conducted a secondary data analysis of 72,060 cases. It conducted frequency analysis, t-test, ANOVA and multiple regression analysis by SPSS 18.0. Although various independent variables influenced on emotional support(t=44.335, p<,001), gender(t=27.730, p<.001), grade(t=25.347, p<.001), economic status(t=-25.345, p<.001), living arrangement(t=-6.158, p<.001), school record(t=-7.512, p<.001), father's educational status(t=-2.378, p<.001), subjective health status(t=46.062, p<.001), depression(t=-23.837, p<.001), sleep(t=19.871, p<.001), level of stress(t=-78.685, p<.001), alcohol(t=-13.481, p<.001) and drug use(t=-2.671, p<.01), smoking(t=-11.988, p<.001), breakfast(t=4.443, p<.001), activity(t=4.757, p<.001) were key factors of subjective happiness among Korean adolescents. The findings of this study were as follow: male middle students, who had emotional support, higher economic status, school record and father's educational level, living with family showed higher levels of subjective happiness. It also having good subjective health status, not depressed, more sufficient sleep, lower stress, no experience of drinking, smoking and drugs, more physical activity and having breakfast showed higher levels of subjective happiness.