An air conditioner may include: a compressor; a condenser; an expander; a bypass pipe that bypasses the refrigerant discharged from the condenser to an inlet side of the compressor; a refrigerant heating apparatus that heats the refrigerant flowing in the bypass pipe; and a valve that controls the refrigerant flowing in the bypass pipe. The refrigerant heating apparatus may include: a refrigerant pipe in which the refrigerant flows; and a heating unit that is provided on an outer surface of the refrigerant pipe and has a carbon nanotube heating element that is heat-generated by itself by a supplied power.