An air conditioner comprising: a heat-source-side unit having a compressor and a heat-source-side heat exchanger; a plurality of use-side units (3a, 3b, 3c, 3d) having a use-side heat exchanger (31a, 31b, 31c, 31d); an intermediate unit that is configured to switch each of a plurality of the use-side heat exchangers (31a, 31b, 31c, 31d) to individually function as an evaporator or a radiator of a refrigerant; and two connection pipes (5, 6) that connect the heat-source-side unit and the intermediate unit, wherein the intermediate unit has an ejector that is configured to pressurize the refrigerant evaporated in one or more use-side heat exchangers (31a, 31b, 31c, 31d) functioning as the evaporator by using a driving flow, and a gas-liquid separator into which the refrigerant flowing out from the ejector flows, the air conditioner being configured such that it is operable in a cooling-heating mixed operation mainly for cooling in which a sum of cooling operation loads of the plurality of use-side units (3a, 3b, 3c, 3d) is greater than a sum of heating operation loads of the plurality of use-side units (3a, 3b, 3c, 3d), wherein the ejector functions in the cooling-heating mixed operation mainly for cooling, wherein the air conditioner further comprises: a first pipe (P411, 51, P31a, P412, 52, P31b, P413, 53, P31c, P414, 54, P31d) that connects the use-side heat exchanger of one of the plurality of use-side units (3a, 3b, 3c, 3d) and the gas-liquid separator; and a second pipe (P415, P416, P417, P418) that branches off from the first pipe and that guides the refrigerant to an inlet of the driving flow of the ejector, wherein the air conditioner being configured such that it is operable in a cooling-heating mixed operation mainly for cooling in which the second pipe guides the refrigerant flowing out from one of the plurality of use-side units (3a, 3b, 3c, 3d) performing heating operation to the inlet of the driving flow of the ejector. a heat-source-side unit having a compressor and a heat-source-side heat exchanger; a plurality of use-side units (3a, 3b, 3c, 3d) having a use-side heat exchanger (31a, 31b, 31c, 31d); an intermediate unit that is configured to switch each of a plurality of the use-side heat exchangers (31a, 31b, 31c, 31d) to individually function as an evaporator or a radiator of a refrigerant; and two connection pipes (5, 6) that connect the heat-source-side unit and the intermediate unit, wherein the intermediate unit has an ejector that is configured to pressurize the refrigerant evaporated in one or more use-side heat exchangers (31a, 31b, 31c, 31d) functioning as the evaporator by using a driving flow, and a gas-liquid separator into which the refrigerant flowing out from the ejector flows, an ejector that is configured to pressurize the refrigerant evaporated in one or more use-side heat exchangers (31a, 31b, 31c, 31d) functioning as the evaporator by using a driving flow, and a gas-liquid separator into which the refrigerant flowing out from the ejector flows, the air conditioner being configured such that it is operable in a cooling-heating mixed operation mainly for cooling in which a sum of cooling operation loads of the plurality of use-side units (3a, 3b, 3c, 3d) is greater than a sum of heating operation loads of the plurality of use-side units (3a, 3b, 3c, 3d), wherein the ejector functions in the cooling-heating mixed operation mainly for cooling, wherein the air conditioner further comprises: a first pipe (P411, 51, P31a, P412, 52, P31b, P413, 53, P31c, P414, 54, P31d) that connects the use-side heat exchanger of one of the plurality of use-side units (3a, 3b, 3c, 3d) and the gas-liquid separator; and a second pipe (P415, P416, P417, P418) that branches off from the first pipe and that guides the refrigerant to an inlet of the driving flow of the ejector, wherein the air conditioner being configured such that it is operable in a cooling-heating mixed operation mainly for cooling in which the second pipe guides the refrigerant flowing out from one of the plurality of use-side units (3a, 3b, 3c, 3d) performing heating operation to the inlet of the driving flow of the ejector. a first pipe (P411, 51, P31a, P412, 52, P31b, P413, 53, P31c, P414, 54, P31d) that connects the use-side heat exchanger of one of the plurality of use-side units (3a, 3b, 3c, 3d) and the gas-liquid separator; and a second pipe (P415, P416, P417, P418) that branches off from the first pipe and that guides the refrigerant to an inlet of the driving flow of the ejector, wherein the air conditioner being configured such that it is operable in a cooling-heating mixed operation mainly for cooling in which the second pipe guides the refrigerant flowing out from one of the plurality of use-side units (3a, 3b, 3c, 3d) performing heating operation to the inlet of the driving flow of the ejector.