PURPOSE: To enable to control discharge of energy under a vent mode, by a method wherein an intake door is made into a two-door structure and one side door is made into an intake opening of indoor air at the time of operation in a cooling cycle under the vent mode.

CONSTITUTION: When a setting device of an intake door is set at FRE, a No.2 door component 9B is located at a position (a) by a cable 34, and then when an automatic control switch 53 and a vent mode switch 58 are turned off a negative pressure is applied to an actuator 37 by actuation of a solenoid valve 60 and a No.1 door component 9A which was at the position (a) is revolved to a position (c). When the setting device of the intake door is set at a neutral position M a door switch 59 is turned off by moving the No.2 door component 9B to a position (b) and the No.1 door component 9A is placed at the position (c) irrespective of a state of the mode switch 59 whether it is turned on or off. When the setting device of the intake door is set at an indoor air circulation position REC the No.1 and the No.2 door components 9A and 9B are moved to the position (c). Discharge of energy is controlled like this, by making one side door into the position where an inflow opening for indoor air is opened at the time of operation in a cooling cycle under a vent mode.