This study is an attempt to comprehend the history and structure of Japanese myth, which has the conflicting characteristic of two opposing ancient myths. The two myths are Takamanohara myth(高天原系神話) centered on Amaterasohomikami(天照大御神) and Izmo myth(出雲系神話) centered on Susanoonomikoto(須佐之男命). The followings are the results of the study intended above. The history of the Japanese myth reveals an important evidence of how the group of ancient Korean immigrants to Japan tried to keep the original Korean Myth in the new environment. And the structure of the myth shows a crucial evidence of conflict and opposition between different groups of immigrants. In other words, the group from Silla(新羅) brought first the farming culture with them. Then, the group from Karak(駕洛) with their hunting culture later, embracing the culture of Silla people, established Yamado(大和) throne. But, in spite of these integration, their two powers cannot make the perfect assimilation. Each of them keep the considerable power, Therefore, the myth reflects the conflict and opposition between the two groups. If this investigation has validity, to some extent, this study will contribute the reconstruction of the system of Korean myth and constitutional process of Korean culture.