The present invention makes it possible to integrate and control in one circuit the systems, such as electric power components, a driving motor, a stack, and an AC condenser which have the maximum enthalpy under similar operational temperature and use conditions, by using an integrated radiator. Therefore, it is possible to minimize air-through resistance of the radiator for cooling the stack and the electric power components and ensure smooth and stable cooling performance of the stack, electric power components, and AC condenser while improving fuel efficiency by reducing the condensation pressure of the air conditioner. Further, it is possible to improve cooling efficiency by non-repeatedly arranging heat exchangers, and reduce the weight of a vehicle, volume of the parts, and the manufacturing cost, by avoiding using too many parts, such as a radiator, a water pump, and a reservoir tank.