An automobile air conditioner includes a duct interconnecting a blower unit and a temperature control/air distributing unit having a pair of cooling and heating heat exchangers, the duct having a cross-sectional area gradually increasing toward the temperature control/air distributing unit. The air conditioner preferably has a hot/refrigeration compartment disposed in juxtaposition with the duct. In a preferred embodiment, the air conditioner includes a hot air control mode door for controlling a stream of hot air flowing from the heating heat exchanger toward an upper air outlet and a lower air outlet.