Deterioration of an electrolyte and a sealing member is suppressed taking account of the durable temperature characteristics thereof, while enhancing the starting performance of a fuel cell. For this realization, in a system comprising a gas piping system for supplying a reactant gas to a fuel cell, and a gas supply controller for altering the supply state of the reactant gas in response to a power generation request, a gas supply quantity is altered in accordance with the temperature of the fuel cell. Preferably, the gas supply quantity is altered in accordance with the durable temperature characteristics of a passage member forming a gas passage of the reactant gas. Furthermore, the differential pressure of the gas supply state between the anode side and the cathode side of the fuel cell is preferably taken into account and the differential pressure between both poles is suppressed by altering the gas supply quantity on the cathode side as the case may be.