An air-conditioning apparatus including a refrigerant circuit formed by connecting, with pipes, a compressor including a compression chamber and an injection port to introduce refrigerant into the compression chamber, the compressor being configured to compress refrigerant and discharge the compressed refrigerant, a first heat exchanger to exchange heat with the refrigerant, a subcooling heat exchanger that includes a first flow passage and a second flow passage and configured to exchange heat between a portion of the refrigerant flowing in the first flow passage and another portion of the refrigerant flowing in the second flow passage to subcool the portion of refrigerant flowing in the first flow passage, a first expansion device to decompress the refrigerant, a second heat exchanger to exchange heat with the refrigerant, and an accumulator connected to a suction side of the compressor and configured to store excess refrigerant, so that the refrigerant is circulated through the refrigerant circuit, the air-conditioning apparatus comprising: a first bypass pipe that connects the second flow passage of the subcooling heat exchanger with a segment of the pipes, the segment being positioned on a refrigerant inflow side of the accumulator; a second expansion device to adjust a flow rate of the refrigerant flowing in the first bypass pipe; a second bypass pipe (4b,4d) that connects a segment of the pipes with the injection port, the segment being positioned between the first heat exchanger and the second heat exchanger; a third expansion device to adjust a flow rate of the refrigerant flowing in the second bypass pipe; a blower device; and an auxiliary heat exchanger arranged at a position which is in vicinity of the first heat exchanger and configured to receive, together with the first heat exchanger, air blown by the blower device and exchange heat with the refrigerant passing through the second bypass pipe (4b,4d) on an upstream side of the third expansion device with respect to a direction of refrigerant flow, characterized in that the auxiliary heat exchanger is arranged below the first heat exchanger, and the air-conditioning apparatus further comprises: an opening and closing device; a hot gas bypass pipe that allows connection between a pipe on a discharge side of the compressor and a segment of the second bypass pipe on a refrigerant inflow side of the auxiliary heat exchanger via the opening and closing device; and a backflow prevention device that is installed on an upstream side of a part of the second bypass pipe that is connected to the hot gas bypass pipe with respect to the direction of refrigerant flow. a first bypass pipe that connects the second flow passage of the subcooling heat exchanger with a segment of the pipes, the segment being positioned on a refrigerant inflow side of the accumulator; a second expansion device to adjust a flow rate of the refrigerant flowing in the first bypass pipe; a second bypass pipe (4b,4d) that connects a segment of the pipes with the injection port, the segment being positioned between the first heat exchanger and the second heat exchanger; a third expansion device to adjust a flow rate of the refrigerant flowing in the second bypass pipe; a blower device; and an auxiliary heat exchanger arranged at a position which is in vicinity of the first heat exchanger and configured to receive, together with the first heat exchanger, air blown by the blower device and exchange heat with the refrigerant passing through the second bypass pipe (4b,4d) on an upstream side of the third expansion device with respect to a direction of refrigerant flow, characterized in that the auxiliary heat exchanger is arranged below the first heat exchanger, and the air-conditioning apparatus further comprises: an opening and closing device; a hot gas bypass pipe that allows connection between a pipe on a discharge side of the compressor and a segment of the second bypass pipe on a refrigerant inflow side of the auxiliary heat exchanger via the opening and closing device; and a backflow prevention device that is installed on an upstream side of a part of the second bypass pipe that is connected to the hot gas bypass pipe with respect to the direction of refrigerant flow. an opening and closing device; a hot gas bypass pipe that allows connection between a pipe on a discharge side of the compressor and a segment of the second bypass pipe on a refrigerant inflow side of the auxiliary heat exchanger via the opening and closing device; and a backflow prevention device that is installed on an upstream side of a part of the second bypass pipe that is connected to the hot gas bypass pipe with respect to the direction of refrigerant flow.