NOVELTY - The device has a cooling water supply line (22) formed in a common distributor (20) of a fuel cell, and a refrigerant supply hole (12) coinciding with an air supply line (24) and an air exhaust line (26). A switching unit conveying passage is formed inside a body portion (10). An air supply hole (14) and an air outlet (16) are formed in the body portion. A switching unit is built in the body portion. The air supply hole and the air outlet are closed when starting a fuel system. A cooling water inflow opening (18) is extended from the refrigerant supply hole of the body portion.    USE - Air electrode opening/closing device for a fuel cell of a vehicle.    ADVANTAGE - The device can block the atmosphere from flowing in the air electrode for long time, and prevents the air from being expanded to the fuel anode. The device can prevent the catalyst corrosion of the air electrode, and can improve the durability and performance of the fuel cell. The device is operated based on the cooling water pressure so that an external motor for opening and closing the air electrode is unnecessary. The device completely opens the manifold opening of the air electrode, so that pressure loss is avoided in airflow and the consumption of power of the air blower is decreased. The entire system efficiency is maintained. The device avoids need of separate space and separate power unit, and enables the fuel system design for layout composition by common distributor of stack. The device is mounted to the common distributor so that the external contamination including the dust is fundamentally isolated for providing durability. The heating apparatus is included in a part closing the airflow line so that the valve operation is smooth even if inlet and outlet of the exhaust line and air-supply are frozen in cold starting condition.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an air electrode opening/closing device.'(Drawing includes non-English language text)'    Body portion (10)    Refrigerant supply hole (12)    Air supply hole (14)    Air outlet (16)    Cooling water inflow opening (18)    Common distributor (20)    Cooling water supply line (22)    Air supply line (24)    Air exhaust line (26)