The fuel cell 60 comprises a proton-conductive, solid electrolyte layer and a hydrogen-permeable metal layer joined to the electrolyte layer. When the fuel cell 60 generates power, reformed gas produced in a reformer 62 is supplied as fuel gas to the anode of the fuel cell 60. When power generation by the fuel cell 60 is stop, air supplied by a blower 67 is fed to the anode of the fuel cell 60, so that the fuel gas within the fuel cell 60 is replaced by air.
