An on-vehicle air-conditioner for air-conditioning has a refrigeration circuit provided with a refrigerant car exterior heat exchanger installed for exchanging heat with the car exterior air that can be used for cooling and for heating, and at least one opening and closing duct for air inflow rate regulation installed in front of and/or behind the refrigerant car exterior heat exchanger. By controlling the opening/closing of the duct according to the situation, the arrangement can solve problems of the prior art, and can efficiently and sufficiently perform cooling, heating, defrosting or the like. The arrangement is useful even when using, for example, CO.sub.2 as a refrigerant, in vehicles such as hybrid cars using electricity and gasoline as their energy source, idle stop coping cars or the like.