A fuel cell power plant comprises a fuel reforming system (1). The fuel reforming system (1) comprises a vaporizer (7) which vaporizes liquid fuel and supplies fuel vapor to a reformer (9). The vaporizer (7) heats injected fuel so as to vaporize it by a heating elements (7A), and supplies it to the reformer (9) via a fuel vapor supply passage (32) comprising a first valve (17). In a standby mode of the vaporizer (7) when the first valve (17) is closed, surplus fuel and heat energy in the standby state are recovered by providing a recovery passage (19, 20) which recovers fuel in the vicinity of the heating elements (7A) to the fuel tank (6) without allowing it to flowing into the vapor supply passage (32).