An air conditioner comprising: a compressor to compress a refrigerant, the compressor having a suction unit and a plurality of injection inlets (11,12,13); an inside heat exchanger into which the compressed refrigerant is introduced during a heating operation; an outside heat exchanger into which the compressed refrigerant is introduced during a cooling operation; a plurality of refrigerant separation devices (50, 60, 70) through which a refrigerant condensed in the inside heat exchanger or the outside heat exchanger pass; a plurality of injection flow paths (51, 61, 71) extending from the plurality of refrigerant separation devices (50, 60, 70) to the plurality of injection inlets (11, 12, 13); and a bypass flow path extending from one of the plurality of injection flow paths (51, 61, 71) to the suction unit wherein the plurality of injection inlets (11, 12) comprises a first injection and a second injection inlet, the plurality of refrigerant separation devices (50, 60) include a first internal heat exchanger and a second internal heat exchanger, and the plurality of injection flow paths (51, 61) includes a first injection flow path and a second injection flow path, characterized in that: the plurality of injection inlets (11,12,13) further comprises a third injection inlet, the plurality of refrigerant separation devices (50, 60, 70) further includes a third internal heat exchanger, and the plurality of injection flow paths (51, 61, 71) further includes a third injection flow path, wherein said first injection flow path is coupled to the first internal heat exchanger to inject a refrigerant having a first intermediate pressure into the compressor; said second injection flow path is coupled to the second internal heat exchanger to inject a refrigerant having a second intermediate pressure into the compressor; and said third injection flow path is coupled to the third internal heat exchanger to inject a refrigerant having a third intermediate pressure into the compressor, and the second intermediate pressure is higher than the first intermediate pressure, and the third intermediate pressure is higher than the second intermediate pressure. a compressor to compress a refrigerant, the compressor having a suction unit and a plurality of injection inlets (11,12,13); an inside heat exchanger into which the compressed refrigerant is introduced during a heating operation; an outside heat exchanger into which the compressed refrigerant is introduced during a cooling operation; a plurality of refrigerant separation devices (50, 60, 70) through which a refrigerant condensed in the inside heat exchanger or the outside heat exchanger pass; a plurality of injection flow paths (51, 61, 71) extending from the plurality of refrigerant separation devices (50, 60, 70) to the plurality of injection inlets (11, 12, 13); and a bypass flow path extending from one of the plurality of injection flow paths (51, 61, 71) to the suction unit wherein the plurality of injection inlets (11, 12) comprises a first injection and a second injection inlet, the plurality of refrigerant separation devices (50, 60) include a first internal heat exchanger and a second internal heat exchanger, and the plurality of injection flow paths (51, 61) includes a first injection flow path and a second injection flow path, characterized in that: the plurality of injection inlets (11,12,13) further comprises a third injection inlet, the plurality of refrigerant separation devices (50, 60, 70) further includes a third internal heat exchanger, and the plurality of injection flow paths (51, 61, 71) further includes a third injection flow path, wherein said first injection flow path is coupled to the first internal heat exchanger to inject a refrigerant having a first intermediate pressure into the compressor; said second injection flow path is coupled to the second internal heat exchanger to inject a refrigerant having a second intermediate pressure into the compressor; and said third injection flow path is coupled to the third internal heat exchanger to inject a refrigerant having a third intermediate pressure into the compressor, and the second intermediate pressure is higher than the first intermediate pressure, and the third intermediate pressure is higher than the second intermediate pressure. the plurality of injection inlets (11,12,13) further comprises a third injection inlet, the plurality of refrigerant separation devices (50, 60, 70) further includes a third internal heat exchanger, and the plurality of injection flow paths (51, 61, 71) further includes a third injection flow path, wherein said first injection flow path is coupled to the first internal heat exchanger to inject a refrigerant having a first intermediate pressure into the compressor; said second injection flow path is coupled to the second internal heat exchanger to inject a refrigerant having a second intermediate pressure into the compressor; and said third injection flow path is coupled to the third internal heat exchanger to inject a refrigerant having a third intermediate pressure into the compressor, and the second intermediate pressure is higher than the first intermediate pressure, and the third intermediate pressure is higher than the second intermediate pressure.