對日本來說，參與區域自由貿易協定最大阻力一直以來主要是來自於農業部門與相關利益團體壓力。因此，面對來自外部壓力要求開放與自由化的同時，日本政府常常不願意在農業部門實施大幅度開放與自由化措施。然而面對TPP 強調高標準、高品質的自由貿易協定，日本政府卻願意加入，其中原因固然是在美國說服下，日本同意加入TPP 談判。日本為何要加入TPP 以及加入TPP 的戰略為何為本文主要的問題意識。本文研究認為，日本政府長期以來面對自由貿易協定的態度常是謹慎且以農業衝擊程度作為考量重點。面對加入TPP，日本政府為了擺脫長期以來經濟停滯不前，振興日本經濟，同時基於美日同盟關係的考量以及中國大陸帶來的競爭壓力，讓日本政府在面對國內農業團體壓力下，仍選擇了加入TPP。

Main obstacle of joint regional free trade agreement is the objection and pressure from Japan agriculture interest groups. Therefore, Japanese government is unwilling to open her agriculture sector when facing extern pressure of demanding open market and free trade. However, why does Japan government agree to joint talks of TPP which a high stander and high quality free trade agreement and what is her strategic thinking are main questions of the paper. The paper's argument is that Japanese government decided to participate in TPP base on three reasons. First of all is promotion Japanese economy. Second is that strengthen alliance relations between Japan and U.S. Third is competing leadership with China in Asia Pacific region. All these reasons make Japanese government joint TPP even facing huge pressure from agriculture interest groups.