Purpose: The purpose of this study is to examine the effect of adolescents' happiness on smartphone dependence for adolescents. Methods: This study was analyzed using panel data of 848 first-year middle school students from the Korean Children, Youth Panel Survey. Result: This study, there were statistically significant differences in sex in women (β=-.086 p=.012), study time for more than 3 hours (β=-.217, p<.001), spare time for more than 1 hour and less than 4 hours (β=.232, p<.001), 4 hours and more (β=.259, p<.001), satisfaction in academic achievement satisfaction (β=-.249, p<.001), exercise for 2 hours (β=.091, p=.020), and happiness in happiness (β=.097 p=.019). These variables represented 14.4% of explanatory power. Conclusion and suggestion: Adolescents should reduce their dependence on smartphones by reducing their smartphones usage time and increasing their happiness by securing study time and using spare time. Therefore, it is necessary to find various ways to reduce dependence on smartphones. We propose a study to develop a program that reduces dependence on smartphones in the future and to understand the effectiveness of the program.