The Northeast Asian sea surrounding South Korea is being discussed in terms of politics, economy and military beyond the geomorphological area. Pan East Sea, where South Korea, North Korea, Japan, Russia and China form the network, initiated from the planning of the economic bloc, but it currently refers to the neighboring countries and the sea area surrounding the East Sea in general. The point that connects the sea area is the port. The marine and land traffic networks stretch out in line with the port as a core. The thesis intends to examine, in overall, the individual subjects from the precedent research. The traffic networks centered on ports, railways and sea lanes are only effective if abundant electricity and port hinterland are formed. In other words, it goes through the process of building power plants to supply electricity, securing a large tract of land to construct the hinterland, and creating the infrastructure such as labor and administration to build a port city. Of course, the budget is mostly funded by the government. This relationship will be studied through the case of Niigata in Japan that played the major role as the East Sea’s traffic network. The Niigata Port rapidly grew along with the expansion of Japanese imperialism in the 1930s and 1940s. The Dalian Port was the central route to connect Japan and Manchuria until 1920, but Japan, which founded Manchukuo in 1932, tried to make the shortest East Sea route between Japan and Manchuria. At that time, Japan observed 新瀉港·伏木港·敦賀港 in Japan and Cheongjin Port·Najin Port·Woonggi Port in the northern part of Joseon. After designating the subsidized line, Japan began expanding port facilities in the Niigata Port and enlarging the city. This was the outcome of traffic network policy for Pan East Sea of imperial Japan.