A fuel cell cooling system includes an air temperature estimating unit, an air temperature sensor and an abnormality determining unit. The air temperature sensor senses an air detection temperature of the air that flows out of the air cooler and is supplied to the fuel cell. The air temperature estimating unit estimates an air estimation temperature of the air, based on a temperature of a refrigerant flowing into the air cooler, a power supply quantity of a power supplied to the circulation pump, a temperature of the air flowing into the air cooler and a flow volume of the air. The abnormality determining unit determines that a circulation flow volume of the refrigerant is in an abnormal state when the air detection temperature is higher than the air estimation temperature by a value greater than or equal to a predetermined value.