NOVELTY - The fuel cell system has oxidizing agent off-gas exhausted from a fuel cell stack (10), to cool refrigerant emitted from an electric compressor (41) and the air in cooling operation mode. The refrigerant emitted from the compressor heats the air for air conditioning, the pressure of refrigerant is decreased, and the refrigerant is heated during heating operation mode of the system.    USE - Fuel cell system for electrical generator for vehicle such as motor vehicle, electric vehicle, marine vessels, etc. Can also be used for portable generator.    ADVANTAGE - The heating efficiency and cooling efficiency in the refrigeration cycle of the fuel cell system can be improved.    DETAILED DESCRIPTION - The fuel cell stack generates electrical energy by electrochemical reaction of combining oxidizing agent gas and fuel gas, compressor compresses the air for use in air conditioning, and heat exchangers (33,34) for heat exchange between outdoor air and refrigerant emitted from compressor and between air and refrigerant respectively. The decompressors (43,46) decrease the pressure of the refrigerant flowing from the heat exchanger (34), and the pressure of the refrigerant compressed by the compressor respectively. A heat exchanger (42) cools the air for the air conditioning by evaporating the refrigerant whose pressure is decreased by the decompressor (43). A heat exchanger (44) heat exchanges between the refrigerant and the oxidizing agent off-gas emitted from the fuel cell stack. The system has a refrigerant passage switch valve (45) to select one of a refrigerant passage for a cooling operation mode and a refrigerant passage for a heating operation mode. The oxidizing agent off-gas exhausted from fuel cell stack, to cool refrigerant emitted from the compressor. The refrigerant is cooled using the outdoor air and passed without being decompressed. The pressure of refrigerant is then decreased, and evaporated to cool the air for use in air conditioning, and the refrigerant is returned to inlet of the compressor, in cooling operation mode of system. The refrigerant emitted from the compressor heats the air for air conditioning, the pressure of refrigerant is decreased, and the refrigerant is heated using the outdoor air and using the oxidizing agent off-gas discharged from the fuel cell stack. The refrigerant is returned to the inlet of the compressor, in the heating operation mode of the system.    DESCRIPTION OF DRAWING(S) - The drawing shows the circuit diagram of the fuel cell system.    Fuel cell stack (10)    Heat exchangers (33,34,42,44)    Electric compressor (41)    Decompressors (43,46)    Switch valve (45)