To cope with the changing international situation in the post Cold-War era, Japan has chosen to be more active in maintaining peace and security in the Asia-Pacific region by strengthening its strategic cooperation with the United States. However, this new stance has forced Japan to face a regional power competition with mainland China. Recently, Beijing and Tokyo have been locked in a dispute over whether the US-Japan defence coopertation should cover the Taiwan area. This paper will examine the basic concept of Japan’s defense policy, Japan’s China policy, and the possible attitude Japan may adopt in the event of a military crisis in the Taiwan Strait.