An air conditioner, comprising: at least one indoor device; an electric heat pump outdoor device connected to the at least one indoor device, configured to drive a first compressor using electric power, and having a first outdoor heat exchanger that performs heat exchange with a refrigerant; a gas heat pump outdoor device connected in parallel with the EHP outdoor device, connected to the at least one indoor device, and including an engine configured to drive a second compressor using a burned gas, a second outdoor heat exchanger that performs heat exchange with the refrigerant, and a waste heat exchanger configured to exchange heat with the refrigerant using waste heat of the engine; and a controller configured to control a warming operation or a defrosting operation of the EHP outdoor device and the GHP outdoor device, and to supply a high pressure refrigerant from the second compressor of the GHP outdoor device to the EHP outdoor device while the EHP outdoor device performs the defrosting operation, wherein the EHP outdoor device includes a first four-way valve, which is switched to an EHP warming mode during which the first compressor is connected with the at least one indoor device when the EHP outdoor device performs the warming operation, and which is switched to an EHP defrosting mode during which the first compressor is connected with the second compressor when the EHP outdoor device performs the defrosting operation, the air conditioner being characterized in that the controller is configured to switch the EHP outdoor device to perform the defrosting operation when it is determined that the first outdoor heat exchanger of the EHP outdoor device is covered with frost while the EHP outdoor device and the GHP outdoor device perform the warming operation by supplying the high pressure refrigerant from the GHP outdoor device to the EHP outdoor device, leading to a two-stage compression cycle in which the high pressure refrigerant from the GHP outdoor device is compressed by the compressor of the GHP outdoor device and then compressed by the compressor of the EHP outdoor device. at least one indoor device; an electric heat pump outdoor device connected to the at least one indoor device, configured to drive a first compressor using electric power, and having a first outdoor heat exchanger that performs heat exchange with a refrigerant; a gas heat pump outdoor device connected in parallel with the EHP outdoor device, connected to the at least one indoor device, and including an engine configured to drive a second compressor using a burned gas, a second outdoor heat exchanger that performs heat exchange with the refrigerant, and a waste heat exchanger configured to exchange heat with the refrigerant using waste heat of the engine; and a controller configured to control a warming operation or a defrosting operation of the EHP outdoor device and the GHP outdoor device, and to supply a high pressure refrigerant from the second compressor of the GHP outdoor device to the EHP outdoor device while the EHP outdoor device performs the defrosting operation, wherein the EHP outdoor device includes a first four-way valve, which is switched to an EHP warming mode during which the first compressor is connected with the at least one indoor device when the EHP outdoor device performs the warming operation, and which is switched to an EHP defrosting mode during which the first compressor is connected with the second compressor when the EHP outdoor device performs the defrosting operation, the air conditioner being characterized in that the controller is configured to switch the EHP outdoor device to perform the defrosting operation when it is determined that the first outdoor heat exchanger of the EHP outdoor device is covered with frost while the EHP outdoor device and the GHP outdoor device perform the warming operation by supplying the high pressure refrigerant from the GHP outdoor device to the EHP outdoor device, leading to a two-stage compression cycle in which the high pressure refrigerant from the GHP outdoor device is compressed by the compressor of the GHP outdoor device and then compressed by the compressor of the EHP outdoor device.