South Korea has one of the highest global suicide rates. In spite of the notorious ranking of suicide rate across the world, analyses of the cause of suicide have been rare in South Korea. Using a Korean survey in 2010 with 399 samples aged 12 to 21, this study conducted structural equation modeling to apply Agnew’s general strain theory to suicidal ideation of adolescents. This study supported the theory’s assumption that negative interpersonal relationship increased suicidal ideation, with mediation effect of depression level. On the other hand, some findings in this study should be questionable. More specifically, negative relationship with friends decreased adolescents’ suicidal ideation. Eventually, however, it increased their suicidal ideation through swelling depression level. In sum, results of this study could help guide to explain the cause of suicidal ideation by interpersonal relationship. In particular, they showed the applicability of general strain theory in South Korea.