本研究主要以新古典現實主義的研究途徑，檢視跨太平洋夥伴關係(TPP)倡議以來，日本民主黨與自由民主黨在國內與國際面向所面臨到的局勢，以此分析對政策發展的影響，並提供合適的解釋，來說明政策轉變的原因。本論文的主要研究步驟如下:首先是理論的部分，針對國際關係主要學派有關外交政策的論點進行辯證;其次，則是簡要說明 TPP 的形成背景與日本相關政策的推動;復次，進一步說明日本歷任內閣對於 TPP 的立場，並討論面臨的課題;最後，再以理論連結決策過程當中的各種事實，導引出本論文的結論以及日本未來 TPP 政策發展可能的變數。

This paper attempts to analyze domestic and international situations faced by the Democratic Party(DP)and the Liberal Democratic Party (LDP)since the TPP was proposed from the neoclassical realism approach. The purpose of this paper is to analyze policy development impacts and explain the necessity of policy changes. This paper will focus on (1) critical thinking of foreign policy from different major international relations theories, (2) backgrounds of TPP development and the push for economic reforms in Japan, as well as position and challenges of former Japanese cabinets on TPP, and(3)possible future development of policies, based on theoretical and fact findings, towards TPP in Japan.