Abstract: This paper proposes a restructuring of multi-layered structure in maintenance works of nuclear power stations in Japan. This multi-layered struc ture had been convenient for the utilities and main venders to keep the many workers in outage and construction period. But in the age of deregulation, de creasing birth rate and aging society, it will become hard to keep this multi-layered structure. One of the measures to deal with this problem is in-house maintenance organized by utility's employees. The Japan Atomic Power Company (JAPC) is now a leading company in this in-house maintenance work in Japan.