This study discusses about Japan's policy to stand in the Trans Pacific Partnership after United States withdrew from membership. The purpose of this study was to find out the internal and external factors that influenced Japan to remain in the TPP after the United States left from the membership. Based on the research that has been done, the author found that Japan's decision to remain in the Trans Pacific Partnership is due to the consideration of domestic politics and international context. From the consideration of domestic politics, there are some incentive from the Liberal Democratic Party and Japan Business Federation that influenced Japanese government to stay in the TPP, while from the consideration of international context, United States’ decision to leave from TPP membership x would actually make Japan become the largest economy in the TPP.