An air conditioner includes a blower unit to blow air at a predetermined amount, a cooling unit arranged downstream of the blower unit in an air flowing direction, a compressor which is operated at a variable operating frequency so that a revolving speed thereof is adjustable, a condenser, and a cooling coil connected in this order by pipes to circulate a heating medium to cool blown air with a heating unit arranged on a downstream side of the cooling unit in the air flowing direction in which the blown air is heated by a heater, and a control unit controls the operating frequency of the compressor and includes a compressor control part which adjusts the revolving speed of the compressor such that the operating frequency of the compressor is decreased by a predetermined frequency when an output of the heating unit exceeds a first threshold value.