AIR CONDITIONER FOR VEHICLE

Frost formation at an outdoor heat exchanger of a heat-pump type air-conditioning system is prevented and an improvement in the heating performance is achieved by efficiently utilizing the heat of the engine cooling liquid. An outdoor heat exchanger 5 and a radiator 9 are each provided with a heat exchanging unit constituted of corrugated fins and a plurality of tubes laminated alternately with the fins and a header communicating with the plurality of tubes, the heat exchanging units of the outdoor heat exchanger 5 and the radiator 9 face opposite each other and the fins are formed as an integrated member shared by the two heat exchanging units. The air-conditioning system for vehicles structured as described above is provided with a means for decision-making that makes a decision as to whether or not the outdoor heat exchanger 5 is in an environment in which frost formation may occur and a means for control that distributes the engine cooling water to the radiator 9 if it is decided by the means for decision-making that the outdoor heat exchanger 5 is in an environment in which frost formation may occur.