An air conditioner is provided. The air conditioner includes a heat exchanger which exchanges heat with air by passing a coolant therethrough; an anti-freeze apparatus which prevents the freeze of water on the surface of the heat exchanger by supplying energy to the heat exchanger; and a heat generation unit which heats the heat exchanger. The air conditioner can minimize the need for a defrost operation and can thus continuously and effectively perform an air conditioning function even when water on the surface of the heat exchanger is frozen.