FUEL CELL SYSTEM

A fuel cell system includes: a steam generator configured to heat water to generate steam; a reforming part configured to cause a reaction between the steam and hydrocarbon to generate a reformed gas containing hydrogen; a fuel cell stack, which has an anode and a cathode, and is configured to generate electric energy through an electrochemical reaction caused between the reformed gas supplied to the anode and an oxidant supplied to the cathode; and an ejector configured to supply at least one of a raw material containing the hydrocarbon or an anode circulating gas obtained by recovering a part of an anode exhaust gas discharged from the anode to the reforming part by using the steam as a driving fluid. The steam generator includes: an evaporation flow passage through which the water flows; an anode exhaust gas flow passage that is thermally connected to the evaporation flow passage and through which the anode exhaust gas flows; and an auxiliary heating device configured to heat the water. The anode exhaust gas flow passage and the auxiliary heating device are opposed to each other across the evaporation flow passage.