An air conditioner for automotive vehicles is disclosed. The flow rates of air supplied to an evaporator (4) and a heater (5) are adjusted by rotationally displacing a scroll casing (2b) and thus changing an air flow from a blower (2) to a predetermined direction. The air-mix door can thus be eliminated to allow a smaller size of an air-conditioner casing (3) (air-conditioning unit (1)). Also, the ratio between cool air flow rate and hot air flow rate is adjusted by rotationally displacing the scroll casing (2b) with a spur gear (2c) and, therefore, the size and the production cost of the air conditioner can be reduced as compared with a conventional system in which an air-mix door is swung by a link mechanism.