PURPOSE: To improve a performance of an air conditioner by immersing a part of a heat exchanger in case of cooling action and to facilitate a discharging of water by a method wherein a door having one end fixed to a rod and the other end with a bellows is arranged at a base plate having U-shaped recess.

CONSTITUTION: When a cooling operation is performed, high pressure coolant is flowed from a compressor through an external heat exchanger 5, passes through a connection pipe 7 and a branch pipe 8 and is fed into the bellows 9. The bellows 9 is extended, the rod 10 is pushed forward, the door 4 is closed, the condensed water is accumulated on the base plate 1, a water level becomes high being increased up to such a level as the water flows out of the water drain hole 4a and so the water level can be adjusted in response to the position of the water drain hole 4a. With this arrangement, it is possible to lift up a linger and then the immersion of the heat exchanger 5 enables a performance of the heat exchanger 5 to be improved. When a heating operation is performed, the high pressure coolant is passed through the external heat exchanger and the capillary tube to generate a low pressure and then fed into the bellows 9. Due to this low pressure, the bellows 9 is retracted under a resilient force of itself, the door 4 is opened, and the condensed water is passed below the fitting of the base plate and then discharged from the drain port 3b.