This article examines the concept of human security form theoretical and historical perspectives. It argues that the emergence of human security is a result of the expansion of roles of public authorities: The growing government's responsibility, its expansion in the social field, and its expansion in the international field. In this regard, human security is not necessarily opposed to national or state security, while they are not always the same. There is a need for comprehensive points of views in the contemporary world, one of which is human security. The historical and political background of Japanese diplomacy explains why the government of Japan has been interested in the concept of human security, although it has not implemented a systematic set of human security oriented policies.