The purpose of this paper is twofold. First, I want to make it clear the source of competitiveness of Japanese main container ports. Second, I will specify the course of suitable container port policy in Japan. In general, there are three sources of competitiveness of container ports, that is, industrial agglomeration and volume of cargoes as the result of it, supply chain networks, especially, networks of shipping lines and stevedoring system in container port. Now, Japanese main container ports have lost the first source of competitiveness of container
ports, namely, volume of cargoes and networks of shipping lines of these ports are weakening. The result clearly show that Japanese main container ports can not depend to increase container cargoes throughput on only efficient stevedoring system in port as the third source of competitiveness of container port. Therefore, Japanese government should, at first, support to strengthen supply chain networks as short-term policy and secondly promote to reagglomerate or regenerate the cluster of manufacturing industry as long-term policy.