AIR CONDITIONER

One of the aspects of the present invention is to provide an air conditioner including an outdoor unit, a plurality of indoor units, and a relay device for connection between the outdoor unit and each of the indoor units. The outdoor unit includes an outdoor heat exchanger, a compressor for pressurizing a refrigerant of carbon dioxide or a composite having main ingredient of carbon dioxide, and a first switching member for switching a flow direction of the refrigerant through the outdoor heat exchanger, which are in fluid communication between first and second connection ends. Each of the indoor units includes an indoor heat exchanger and a first flow controller which are in fluid communication between first and second pipe connection ports. The relay device includes a plurality of second switching members, each of which the second switching members selectively connects the first pipe connection port of the respective indoor unit with the first or second connection end of the outdoor unit. The relay device also includes a first bypass pipe for connection between the second connection end of the outdoor unit and each of the second pipe connection ports of the indoor units, and a second flow controller intervening in the first bypass pipe.