The economic relation of korea and Japan has developed from dependent pattern to interdependent or competitive one under the changes of economic surroundings. In this paper, we addresses the economic relation for 65 years after the Second World War, with aim to prospect for future cooperation pattern between the too. The study focuses on identifying Japan`s role on the economic growth or fluctuation of Korea, and on reverse pattern. The result can be summarized a follows: First, the volume of Korea-Japan trade increased dramatically. We can, however, witness that Japan`s weight in total Korean trade and Korea`s weight in Japan also are decreasing. Besides China`s economic growth, the diffusion of international production division in underdeveloped countries in Asia mainly comes to have the two economies being non-dependency. Second, Characteristics in Korea-Japan economic relation for 65 years can be summarized: 1) Japan as an external economy in Korea`s economic growth and export increase to Japan, 2) Japan`s non-tariff barriers and Korea`s sluggish exports to Japan, 3) Korea as an indirect export of Japan, 4) The closure of the Japan`s dome tic market and deepening competitive industrial structure of the two economies, 5) The relative collapse balance of the two in the volume of trade, 6) The excessive competition structure in overseas markets and the deterioration of terms of trade. Third, the study intend to highlight the closure of Japanese market as one of overlooked factors why the economic relation developed to be competitive. This gradual transformation has the possibility to bring overcompetition and welfare loss eventually. We might prospect the transnational corporative competition among companies in both countries, accelerated by IT A.