This book analyzes the institutional origin and evolutional process of Japan's so-called developmental state system from a historical institutionalist point of view. Many studies of the Japanese postwar economy suggest that the developmental state system played an important role in Japan's rapid economic growth. Japan's developmental state system consists of such institutions as a highly effective bureaucratic system that planned and orchestrated high speed industrialization and industrial associations that facilitated collaboration between the state and the private sector. A careful analysis of the history of Japanese political economy shows that many of these institutions emerged during the war and continued to function as the core of the Japanese developmental state system for an extended period of time. That is to say, the path of institutional evolution of the Japanese developmental state system institutions depended heavily on the ideas and policies made before the end of WWII. In spite of the significance of these institutions in the Japanese economy, their evolutional process has not been fully investigated in existing studies. In other words, we know that those institutions were important, but we do not know where they came from and how and why they were built.