A fuel cell system includes a fuel cell for generating power by being supplied with a fuel gas and an oxidizing gas, a fuel gas supply path for supplying a fuel gas to the fuel cell, a fuel off-gas circulation path for returning a fuel off-gas discharged from the fuel cell to the fuel gas supply path, an ejector, provided in the fuel gas supply path and driven by fluid flow energy, for supplying the fuel off-gas in the fuel off-gas circulation path flow to the fuel gas supply path, a fuel pump, provided in the fuel off-gas circulation path or on the fuel gas supply path and downstream with respect to the ejector, and driven by a rotating machine, for pressurizing the fuel off-gas, a discharge valve for discharging the fuel off-gas from the fuel off-gas circulation path; and a control device operatively connected to the fuel pump and to the discharge valve.