Both interpersonal stressors and personality traits are thought related to the pathogenesis of depressive states of young adults in Japan. This study examined the relationship among depressive states, interpersonal stressors and personality traits of university student by using the Japanese Version of the Depressive States Checklist revised (J-DSC-R; Hasegawa.et.al, 2010), Interpersonal Stressor Scale (Hashimoto, 2005, partial change), and Big Five Scale (Wada, 1996). Eventually, 243 valid responses were sampled. Multiple regression analysis of the data indicated that the Big Five personality traits accounted for 36% of depressive states. In particular, Neuroticism, one of the Big Five factors, had significant impact on both interpersonal stressors and depressive states. On the other hand, interpersonal stressors accounted only for 4% of depressive states. The same relationship between Neuroticism and depressive states were observed in the higher interpersonal stressor group. These results suggest depressive states may be attributed to the Big Five personality traits rather than interpersonal stressors. This finding may contribute to the development of psychological intervention against depressive state, a risk of depressive disorder, of university students.