This report examined the transport capacity reinforcement of Japanese National Railways (JNR) and the construction process of the Shinkansen (Japanese high-speed railway) and considered the socioeconomic influence that this “technique revolution” brought during the high-speed economic growth period of Japan. Postwar Japan experienced the domestic demand circulation-centered high-speed growth from 1955. With it, the railroad transport volume increased remarkably. To cope with this situation, JNR carried out the railroad capacity reinforcement five-year plan which will keep step with the national income doubling plan. Among the projects of JNR, the construction of Tokaido Shinkansen was promoted as the biggest project. The opening of Tokaido Shinkansen brought the time production effect, the expansion of the one day travelable area, and the regional concentration of economic power, that is, the acceleration of regional disparity. However, the deterioration of the competitiveness was unavoidable in the non-Shinkansen route and the freight transport sector. The construction of the Shinkansen was not able to guarantee the stabilization of JNR management itself.