PURPOSE: To achieve favourable battery cooling, so as to improve reliability of the battery in respect to leakage of the cooling medium, by providing only one inlet and outlet of the cooling medium to the tube which is passed through the cooling plate.

CONSTITUTION: The cooling medium is supplied from a cooling medium supply tube 9 into a cooling tube 7, absorbs the generated heat of the fuel cell, and discharged out of the system to the outside by a cooling medium exhaust tube 10. As the cooling tube 7 is essentially constructed from one tube, the whole amount of the cooling medium supplied from the cooling medium supply tube 9 flows the cooling tube 7. Thus, in this system, ununiform flow distribution of the cooling medium is avoided and cooling of the battery can be carried out smoothly, unlike the system having a plurality of cooling tubes. Furthermore, as the cooling tube 7 is connected only to two tubes, namely to the cooling medium supply tube 9, and the cooling medium exhaust tube 10, the generation of leakage of the medium is greatly reduced.