This study verified the moderating effect of interpersonal competence in relationship between academic performance and happiness. To this end, this study conducted a survey using structured questionnaires that employed subjective evaluation of academic performance, concise measure of happiness, and measure of interpersonal competence, with 442 high school students in Daegu and Gyeongsangbuk-do as subjects, from August 14 to 29, 2017. The results of this study are as follows. First, analysis of relationship among each variable showed that happiness and interpersonal competence had static correlation. Second, academic performance had static effect on happiness. In other words, the higher a student’s academic performance, the happier he was. Third, interpersonal competence had static effect on happiness. That is to say, the stronger a student’s interpersonal competence, the happier he was. Fourth, the effect of academic performance on happiness was moderated by interpersonal competence. In other words, when academic competence was high, the subject’s level of happiness was higher compared to when his interpersonal competence was weak if interpersonal competence was strong. To examine each sub-factor, formation of relationship had a moderating effect but expression of opinions, understanding and consideration, and self-openness did not have a moderating effect. This study verified that academic performance and interpersonal competence had static influence on an adolescent’s happiness, and interpersonal competence was able to moderate the effect of academic performance on happiness.