To maintain the inside of an air flow passage of a fuel cell at the optimum humidity without increasing the number of parts.

Based on an entrance temperature T1 of the air supply manifold detected by a first temperature sensor 71 and on a power generation current capacity I of the fuel cell 10 detected by the inverter 50, the fuel cell system calculates respective target temperatures T2*, T3* of the entrance of a heat medium supply manifold and the exit of a heat medium exhaust manifold, and then controls a first and a second pumps 74, 75 so that the entrance temperature of the heat medium supply manifold and the exit temperature of the heat medium exhaust manifold become the target temperatures T2* and T3*.

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