A heat exchange system for realizing an adequate heat exchange among a plural type of fluids uses a refrigerant radiator and a radiator which are combined to have one unit for enabling heat exchange between a refrigerant and a coolant, and decreases an inflow amount of the coolant flowing into the radiator when coolant temperature of the coolant flowing into the radiator is equal to or higher than a second standard temperature, which is set to be lower than a temperature of the refrigerant flowing into the refrigerant radiator, and is equal to or lower than a predetermined first standard temperature. In such manner, heat from the refrigerant is effectively transferred to an outside air by reducing an unwanted heat exchange between the refrigerant and the outside air.