Abstract: A fuel cell system controls an amount of cooling water supplied to a radiator and an amount of cooling water supplied into a radiator bypass pipe by regulating a temperature of a thermostat valve by controlling a temperature of a heat medium in a housing by an air conditioning apparatus.

Abstract: A fuel cell system comprises: a fuel cell stack; a cooling water supply pipe as a circulation path for cooling water, connected to a cooling water passage in the fuel cell stack; a radiator arranged in the cooling water supply pipe; a radiator bypass pipe that is arranged in the cooling water supply pipe and used for allowing cooling water to bypass the radiator; a cooling water pump arranged in the cooling water supply pipe; a thermostat valve configured to control the amount of cooling water supplied to the radiator and the radiator bypass pipe depending on temperature; a housing surrounding the thermostat valve; an ion exchanger arranged in the radiator bypass pipe; and an air conditioning apparatus configured to supply a heat medium to the housing.