An air conditioner comprising: an inverter section applying an operation power source to a motor of a compressor; and a control section controlling the air conditioner so that the compressor is normally operated if a preheating operation condition of the compressor is not satisfied, so that the compressor enters a preheating operation condition, in which a predetermined current is applied to the motor of the compressor, if the preheating operation condition of the compressor is satisfied, and so that the compressor is released from the preheating operation condition if a preheating releasing condition is satisfied, characterised in that: whether the preheating operation condition of the compressor is satisfied is determined according to exterior temperature, discharge temperature of the compressor, and operation state of the compressor, whether the preheating releasing condition is satisfied is determined according to the exterior temperature, the discharge temperature of the compressor, and the operation state of an indoor unit of the air conditioner during the preheating operation, the preheating operation condition of the compressor is satisfied when the exterior temperature is below a first preheating reference temperature, and the discharge temperature of the compressor is below a second preheating reference temperature, and the compressor is turned off; and the preheating releasing condition of the compressor is satisfied when the exterior temperature is above a first preheating releasing temperature, or the discharge temperature of the compressor is above a second preheating releasing temperature, or the indoor unit is operated. an inverter section applying an operation power source to a motor of a compressor; and a control section controlling the air conditioner so that the compressor is normally operated if a preheating operation condition of the compressor is not satisfied, so that the compressor enters a preheating operation condition, in which a predetermined current is applied to the motor of the compressor, if the preheating operation condition of the compressor is satisfied, and so that the compressor is released from the preheating operation condition if a preheating releasing condition is satisfied, characterised in that: whether the preheating operation condition of the compressor is satisfied is determined according to exterior temperature, discharge temperature of the compressor, and operation state of the compressor, whether the preheating releasing condition is satisfied is determined according to the exterior temperature, the discharge temperature of the compressor, and the operation state of an indoor unit of the air conditioner during the preheating operation, the preheating operation condition of the compressor is satisfied when the exterior temperature is below a first preheating reference temperature, and the discharge temperature of the compressor is below a second preheating reference temperature, and the compressor is turned off; and the preheating releasing condition of the compressor is satisfied when the exterior temperature is above a first preheating releasing temperature, or the discharge temperature of the compressor is above a second preheating releasing temperature, or the indoor unit is operated. whether the preheating operation condition of the compressor is satisfied is determined according to exterior temperature, discharge temperature of the compressor, and operation state of the compressor, whether the preheating releasing condition is satisfied is determined according to the exterior temperature, the discharge temperature of the compressor, and the operation state of an indoor unit of the air conditioner during the preheating operation, the preheating operation condition of the compressor is satisfied when the exterior temperature is below a first preheating reference temperature, and the discharge temperature of the compressor is below a second preheating reference temperature, and the compressor is turned off; and the preheating releasing condition of the compressor is satisfied when the exterior temperature is above a first preheating releasing temperature, or the discharge temperature of the compressor is above a second preheating releasing temperature, or the indoor unit is operated.