To provide a vehicular air conditioner capable of quickly increasing the temperature of engine cooling water with a simple structure even in the early stage of an engine start or the like at low outside air temperature in the case of heating the interior of a vehicle by means of the engine cooling water.

The vehicular air conditioner includes: a second refrigerant circulation pipe line 9b which is connected to a flow passage for connecting a compressor 11 with a three-way solenoid selector valve 13 so as to bypass a condenser 14, an expansion valve 16, and an evaporator 7a; a water-refrigerant heat exchanger 25 which executes heat exchange between a gaseous refrigerant discharged from the compressor 11 through the second refrigerant circulation pipe line 9b by means of the flow passage switching operation of the three-way solenoid selector valve 13, and the engine cooling water which flows into the side of a heater-core 8a in a cooling water circulation circuit 10 for heating; and an expander 21 which is provided in a flow passage between the water-refrigerant heat exchanger 25 and the compressor 11 along the refrigerant circulation direction in the second refrigerant circulation pipe line 9b, and which reduces the pressure of a gas-liquid two-phase refrigerant condensed by executing the heat exchange in the water-refrigerant heat exchanger 25 so as to change the phase thereof into the gaseous refrigerant.