It has heretofore been practiced upon the occurrence of abnormalities on the equipment to make tentative conditioned operation disregarding abnormalities on the assumption that the abnormalities shall be coped with by servicemen. Thus, troubles having insignificant contents of abnormality could not be readily coped with by a simple method. There are provided a fuel cell, a fuel gas supplying unit, an oxidizer gas supplying unit, a state detecting unit of detecting the temperature of the fuel gas supplying unit, an operation controlling unit of detecting abnormalities of predetermined functions performed by the fuel gas supplying unit utilizing the results detected by the state detecting unit and performing operation control in an operation mode corresponding to the contents of abnormalities, and an operation mode switching unit of switching to an operation mode corresponding to the contents of abnormalities.