The present invention relates to a fuel cell system that performs power generation by supplying anode gas and cathode gas to a fuel cell and which comprises: a control valve that controls the pressure of the anode gas in the fuel cell; a buffer unit that stores an anode off-gas which is discharged from the fuel cell; an off-gas discharge passage that connects the fuel cell with the buffer unit; a purge passage that is connected to the off-gas discharge passage; a purge valve that is disposed in the purge passage; purge means that open the purge valve to discharge the gas in the buffer unit out of the fuel cell system; and pressure control means that cause the gas in the buffer unit to flow backward to the fuel cell side by lowering the pressure of the anode gas in the fuel cell from a first predetermined pressure to a second predetermined pressure.
