To improve the comfortableness by further preventing the cold air supply when the heating operation is started or during the defrosting operation by an air conditioner.

In a heating operation of an air conditioner capable of automatically controlling the direction of an air direction plate arranged at an outlet of an indoor unit, an indoor unit control device 10 controls an indoor fan part 5 to weaken the supply of the hot air to perform the cold air preventive action when the temperature of an indoor heat exchanger detected by the detection signal of a heat exchange temperature sensor part 4 is lower than the prescribed value from the start of operation. In the cold air preventive action, an air direction plate part 6 is controlled and a vertical air direction plate is directed to a downward supply orientation to prevent the cold air supply. When the cold air preventive action is performed, the vertical air direction plate is directed further inwardly of a body than the downwardly supplying condition (inwardly and downwardly supply direction). When the temperature of an indoor heat exchanger exceeds the prescribed value, the cold air preventive action is released, and the vertical air direction plate is return as it is preset.