An air conditioner comprising: a refrigerant circuit that includes an outdoor unit and a plurality of indoor units and is able to perform a refrigeration cycle in which a cooling operation and a heating operation are performed in parallel with each other, wherein the air conditioner includes a plurality of operation switching units, each of which is connected to an associated one of the indoor units through two indoor communication pipes (13, 14) and changes directions of refrigerants flowing through the indoor communication pipes (13, 14) in response to a switch made by the indoor unit from a cooling operation to a heating operation, and vice versa, characterized in that a gas-liquid separation unit with which the operation switching units are connected in parallel with each other through three intermediate communication pipes (15, 16, 17) comprised of two gas pipes and one liquid pipe, which is connected with the outdoor unit through two outdoor communication pipes (11, 12), and which is provided separately from the operation switching units, the operation switching units each include a flow channel switching circuit that switches flow channels of a liquid refrigerant and a gas refrigerant between the intermediate communication pipes (15, 16, 17) and the indoor communication pipes (13, 14), and the gas-liquid separation unit includes a gas-liquid separator and a refrigerant flow channel switching circuit that switches flows of a liquid refrigerant and a gas refrigerant in the intermediate communication pipes (15, 16, 17). a refrigerant circuit that includes an outdoor unit and a plurality of indoor units and is able to perform a refrigeration cycle in which a cooling operation and a heating operation are performed in parallel with each other, wherein the air conditioner includes a plurality of operation switching units, each of which is connected to an associated one of the indoor units through two indoor communication pipes (13, 14) and changes directions of refrigerants flowing through the indoor communication pipes (13, 14) in response to a switch made by the indoor unit from a cooling operation to a heating operation, and vice versa, characterized in that a gas-liquid separation unit with which the operation switching units are connected in parallel with each other through three intermediate communication pipes (15, 16, 17) comprised of two gas pipes and one liquid pipe, which is connected with the outdoor unit through two outdoor communication pipes (11, 12), and which is provided separately from the operation switching units, a plurality of operation switching units, each of which is connected to an associated one of the indoor units through two indoor communication pipes (13, 14) and changes directions of refrigerants flowing through the indoor communication pipes (13, 14) in response to a switch made by the indoor unit from a cooling operation to a heating operation, and vice versa, characterized in that each of which is connected to an associated one of the indoor units through two indoor communication pipes (13, 14) and changes directions of refrigerants flowing through the indoor communication pipes (13, 14) in response to a switch made by the indoor unit from a cooling operation to a heating operation, and vice versa, characterized in that a gas-liquid separation unit with which the operation switching units are connected in parallel with each other through three intermediate communication pipes (15, 16, 17) comprised of two gas pipes and one liquid pipe, which is connected with the outdoor unit through two outdoor communication pipes (11, 12), and which is provided separately from the operation switching units, with which the operation switching units are connected in parallel with each other through three intermediate communication pipes (15, 16, 17) comprised of two gas pipes and one liquid pipe, which is connected with the outdoor unit through two outdoor communication pipes (11, 12), and which is provided separately from the operation switching units, the operation switching units each include a flow channel switching circuit that switches flow channels of a liquid refrigerant and a gas refrigerant between the intermediate communication pipes (15, 16, 17) and the indoor communication pipes (13, 14), and a flow channel switching circuit that switches flow channels of a liquid refrigerant and a gas refrigerant between the intermediate communication pipes (15, 16, 17) and the indoor communication pipes (13, 14), and the gas-liquid separation unit includes a gas-liquid separator and a refrigerant flow channel switching circuit that switches flows of a liquid refrigerant and a gas refrigerant in the intermediate communication pipes (15, 16, 17). a gas-liquid separator and a refrigerant flow channel switching circuit that switches flows of a liquid refrigerant and a gas refrigerant in the intermediate communication pipes (15, 16, 17).