PURPOSE: To prevent offensive odor by placing a change-over door at a position where the amount of air attaining an evaporator is reduced in accordance with an OFF signal of an ON-OFF switch for an air conditioner to reduce the amount of air in contact with the evaporator so that air flows from a bypass to the downstream of the evaporator.

CONSTITUTION: When a switch 17 is turned OFF to stop applying voltage to a motor for a blower fan 3, an OFF signal allows a change-over door 13 to be changed by an actuator 14 from the second position 13b to the first position 13a as shown by a solid line to open the opening 12a of a bypass 12 and served as a baffle on the upstream of an evaporator 5. So, air A which flows onto the evaporator 5 with high air resistance and offensive odor is reduced and still almost air B flows to the downstream of the evaporator 5 via a bypass 12 with low resistance. As a result, less offensive odor is carried by the idle running blower fan 3 to an inside PR.