The purpose of this paper is to clarify of the “Asian character" of Asian regionalism by analyzing the political process of the ADB foundation. It examines how Asian nations understood the relationship between nationalism and regionalism, and how the insistence of the ""Asian character"" of the ADB was projected onto the process. For the developing countries in Asia, the regional cooperation association did not necessarily mean adjustment or promotion of a common development project of the region. In fact, it means reservation of influential voice of each country. On the other hand, Japan aimed at improvement of the status in international society by taking leadership in foundation of the ADB. But it could not respond to the demand to North South problem solution of regional countries, and was not able to meet the expectation of Asian nations for its own country, either. Therefore, Japan which is the only advanced country in this region could not utilize its position well and lacked a role of a balancer deterministically. These differences in the expectation between Asian developing countries and Japan also expressed the limit of the regional cooperation of the 60s as it was.