To perform dehumidifying operation causing no drop in room temperature even under a low temperature condition of outside air; and to perform dehumidifying operation causing no reduction in heat exchange efficiency in the dehumidifying operation for circulating a refrigerant in the same direction as cooling operation.

This air conditioner has a compressor for compressing the refrigerant, an indoor heat exchanger for exchanging heat between the refrigerant and indoor air, a pressure reducing device for decompressing or throttling the refrigerant, an outdoor heat exchanger for exchanging heat between the refrigerant and the outside air and an auxiliary heat exchanger arranged between the indoor heat exchanger and the pressure reducing device, passing the refrigerant through in air-conditioning and heating operation and performing the same action as the outdoor heat exchanger in the dehumidifying operation, and has an outdoor heat exchanger bypassing circuit having one end connected to a pipe between the compressor and a four-way valve and having the other end connected to a pipe between the pressure reducing device and the indoor heat exchanger, and has an opening-closing valve for adjusting a flow rate of the refrigerant of the bypassing circuit according to the outside air temperature.