at least two blowoff duct which discharge conditioning air into a car interior have separate individual channels . at least one of the blowoff ducts is a main duct which communicates with a heating device or a cooling device , and the remaining ducts are auxiliary ducts . a heat conductor is arranged in each blowoff duct and the heat conductors are connected conductively by a heat pipe . heat energy of the conditioning air in the main duct which was heated by the heating device or cooled by the cooling device is transmitted to conditioning air in the auxiliary duct by the heat pipe and heat conductors so as to heat or cool the air in the auxiliary duct . the heat pipe may be made to be rotatable by a driving device , and a heat conductor in the auxiliary duct is a blowing fan . air conditioning to the area surrounding a rear seat is achieved by arranging a heat pipe between right and front seats in the car interior and by forming a heat conductor at the rear end of the blowing fan .