PURPOSE: To improve ease of operation when an intake door is in the external air intake position and a signal for setting the door to the internal air circulation position is inputted again by setting the intake door to the internal air circulation position until the same signal is further inputted.

CONSTITUTION: The setting position of an intake door 5 is controlled by a means 100 according to the calculated value of a means 100 for calculating indoor heat load signals. If the intake door 5 is set to an internal air circulation position while the intake door 5 is in an external air intake position, the intake door 5 is controlled by a means 120 so that the door is switched to the internal air circulation position for a specified period of time. When the intake door 5 is set again to the internal air circulation position while the means 120 is working, the intake door 5 is switched to the internal air circulation position. When a signal is further inputted to set the intake door to the internal air circulation position under the above condition, a means 130 controls to cancel the setting to the internal air circulation position.