The Cabinet Planning Board (CPB : October 1937-November 1943) continued for the longest period and was the most extensively developed office of the so-called "Offices for the Integration of National Policy" (OINP). These offices were established to strengthen the Cabinet in the period of the post-Party Cabinets in Japan. Moreover, the CPB continued throughout one of the most important periods of the Japanese modern history, from the Sino-Japanese War to the Pacific War. Accordingly, we must examine the actual condition of the CPB in order to study the decision making process of national policy during that period. But the image that is derived from past studies about the formation process of the CPB is that it was simply "an Office for General Mobilization" (OGM) or was "weak". This image does not coincide with that of an "active" CPB in the period of the Konoe New Organization (Konoe Shin-taisei) in 1940. Therefore, the author describes the actual condition of CPB from October 1937 to the end of 1939 in this paper. The CPB was established as a result of the amalgamation of the Resources Bureau (Shigen-kyoku) as OGM and the Cabinet Planning Agency (Kikaku-cho) as OINP. The Army had taken the lead in establishing it. But it still maintained the "structual" weak point of OINP. The CPB did not have authority over the other government offices. But the weak point was overcome through the roles which the CPB was allowed to play during the Sino-Japanese war. It planned the National General Mobilization Plans (Kokkasodoin-keikaku), which were at the heart of the Material Mobilization Plans (MMP ; Butsudo-keikaku), and it spearheaded the application of the National General Mobilization Law. The CPB was the real power behind the National General Mobilization Business Committee which organized each ministry for the purpose of mobilization, and the CPB also established the Temporary Materials Coordination Bureau as a external unit of the Ministry of Commerce and Industry for the application of MMP. The CPB also held the real power of making the budget for the subdivision of MMP around the first half 1939. That is, the CPB became the center of "the System for the application of the Mobilization Law" which included the National General Mobilization Council. Moreover, the CPB was closely connected with the establishment and operation of government offices for the National General Mobilization in the broad sense of the word. These offices included the Second Committee, the Third Committee, the Science Council (Kagaku-shingikai), the East-Asian Laboratory (Toa-kenkyujo), and the Asian Developement Board (Koa-in). And the CPB came to control a group of government offices which should be called "the CPB System". In order to see how much political influence the CPB had in the "circumstantial" sense, the author concentrates on two issues : 1)the expansion of the CPB from the autumn of 1938 to the spring of 1939 ; and 2)the establishment of the Trade Ministry in the autumn of 1939. It became clear that CPB had more considerable political influence over the contemporary political scene as the proposer and promoter of "reformatory" policies. However the outcome of these two issues was not as the CPB and the Army had expected or wished. The CPB was not simply an OGM. Besides, such CPB actions were caused by some of "the Reformists" among the bureaucrats and military officers who served in CPB. "The Reformists" increasingly entered the CPB through "the CPB System".