PURPOSE: To facilitate wind temperature control at the time of a bi-level by controlling a device in a blow-off mode with combined doors while providing a bypath and upper and lower blow-off ports all equipped with the doors on a heater unit provided with a heater core therein, in a reheat type air conditioner.

CONSTITUTION: Air cooled by an evaporator is introduced into a heater unit 3. The opening/closing of doors 16, 18, 19, 22 is controlled according to a mode selected by a mode selecting lever 26. For example, in the upper part mode, the upper part door 18 and the control door 16 are opened, and the lower part door 19 and the defrost door 22 are closed. Hereby, a blow-off warm wind from a heater core 10 adjusted in its amount of heating by a warm water flow rate control valve 13 and a cool wind on a side passage 17 mixed together are blown off from a upper part blow-off port 20. The doors are combined and controlled in each mode as shown in the drawing. With this constitution, it is possible to easily obtain highly accurate blow-off wind temperature from upper and lower blow-off ports 20, 21 at the bi-level mode.