The air conditioner of the present invention comprises: an external panel which forms an external appearance; a housing having an opening formed on the external panel; a heat exchanger which exchangesheat with air introduced into the housing; and a door unit which moves to the front or back side of the opening through which the heat-exchanged air is discharged, thereby opening or closing the opening, wherein the door unit comprises: a door blade for opening and closing the opening; a door operation unit for moving the door blade forward or backwards; and a control unit for adjusting the separation distance between the door blade and the opening to control the air discharged from the opening to go straight forward to the front side of the opening or to be discharged radially from the opening.