AIR CONDITIONER

PROBLEM TO BE SOLVED: To provide an air conditioner which can strike a balance between a heating operation and a defrosting operation without impairing amenity.SOLUTION: The air conditioner includes: an indoor heat exchanger 4 for exchanging heat between indoor air and a refrigerant; an expansion valve 5 for decompressing the refrigerant; an outdoor heat exchanger 6 for exchanging heat between outdoor air and the refrigerant; a compressor 7 for compressing the refrigerant; a four-way valve 8 for switching the forward and backward directions of a refrigerant channel; and an indoor fan 9 for sending air into a room. In a refrigeration cycle, the refrigerant flows into the compressor 7, the four-way valve 8, the indoor heat exchanger 4, the expansion valve 5, the outdoor heat exchanger 6, and the four-way valve 8, in that order, upon the heating operation. The air conditioner has functions of an automatic cleaning operation for automatically cleaning an air filter 11 and of a defrosting operation by switching the four-way valve 8, and simultaneously performs the defrosting operation and the automatic cleaning operation.