An air conditioning apparatus includes a valve for selectively introducing the coolant discharged from a compressor to either a flow path for a water-coolant heat exchanger or another flow path to avoid the heat exchanger, a thermostat for detecting the temperature of a cooling water flowing into an engine and a controller for controlling the valve. When the temperature of the cooling water is equal to or less than a predetermined temperature, the controller controls the valve so that the coolant discharged from the compressor is introduced to the water-coolant heat exchanger. When the temperature of the cooling water is more than the predetermined temperature, the controller controls the valve so that the coolant discharged from the compressor avoids the water-coolant heat exchanger.