A fuel cell system includes: a fuel cell; a fuel treating unit configured to treat a raw fuel and generate fuel gas for the fuel cell; an oxidant-gas heater configured to heat oxidant gas for the fuel cell; a combustor configured to combust the raw fuel and generate combustion gas to heat the fuel treating unit and the oxidant-gas heater; and a control unit configured to control supplying of the raw fuel to the fuel treating unit and the combustor at the time of warming-up of the fuel cell. The control unit supplies the raw fuel to both of the fuel treating unit and the combustor when the fuel treating unit is at an operable temperature of the fuel treating unit.