Thermoelectric power generation technology has been recognized to contribute to the realization of environment-friendly society all over the world in the future. Present status and future prospects on the thermoelectric power generation technology in Japan are overviewed. The thermoelectric applications for power generation have been mainly considered to be one of the waste heat recovery systems from industrial, private, and transportation sectors in the Japanese energy system. Such activities have been in progress in Japan. Then, several demonstration system tests and feasibility study have been achieved using practical heat sources such as industrial furnaces, motorcycles, solid waste incinerators, and solar thermal systems have been achieved mainly by private companies. Several topics of experimental results on advanced modules based on layered oxides, Heusler alloys, filled Skutterudites for power generation from the view points from environment-friendly and nanostrucuture approach are included. In the future prospects the recent R&D projects of advanced materials for thermoelectric power generation technology and the commercialization of thermoelectric power generation applications are discussed.