A multi-room air-conditioning apparatus comprising: - an outdoor unit that includes at least a compressor, a switching valve, and an outdoor-unit-side heat exchanger; - a relay unit that is connected to the outdoor unit by a first connection pipe and a second connection pipe; and - a plurality of indoor units, each of which includes an indoor heat exchanger and a first flow control device and which are connected to the relay unit while being arranged in parallel, - wherein the outdoor unit includes a first route along which a refrigerant that is discharged from the compressor is guided to the second connection pipe via the switching valve and the outdoor-unit-side heat exchanger, and a second route along which the refrigerant is guided to the second connection pipe via the switching valve while bypassing the outdoor-unit-side heat exchanger, so that the refrigerant is guided in accordance with operation modes including a cooling operation mode, a heating operation mode, a cooling main operation mode, and a heating main operation mode, - wherein the relay unit includes a first gas-liquid separating device that is connected to an intervening portion of the second connection pipe, a plurality of switching units (104: 12a, 13a; 12b, 13b; 12c, 13c) that individually connect the indoor units to one of the first connection pipe and the second connection pipe selectively, a first bypass pipe that connects the first gas-liquid separating device to each of the indoor units, a second bypass pipe that connects the first connection pipe to the first bypass pipe, a third flow control device provided to the first bypass pipe, and a second flow control device provided to the second bypass pipe, and wherein the multi-room air-conditioning apparatus is characterized by further comprising: - a second gas-liquid separating device provided between the outdoor unit and the relay unit and connected to the first connection pipe; - a gas-side outlet pipe that allows a gas refrigerant generated by gas-liquid separation performed by the second gas-liquid separating device to bypass the outdoor-unit-side heat exchanger and to flow into a refrigerant suction port of the compressor; and - a liquid-side outlet pipe that bypasses a liquid refrigerant generated by the gas-liquid separation performed by the second gas-liquid separating device to flow into the refrigerant suction port of the compressor via the outdoor-unit-side heat exchanger. - an outdoor unit that includes at least a compressor, a switching valve, and an outdoor-unit-side heat exchanger; - a relay unit that is connected to the outdoor unit by a first connection pipe and a second connection pipe; and - a plurality of indoor units, each of which includes an indoor heat exchanger and a first flow control device and which are connected to the relay unit while being arranged in parallel, - wherein the outdoor unit includes a first route along which a refrigerant that is discharged from the compressor is guided to the second connection pipe via the switching valve and the outdoor-unit-side heat exchanger, and a second route along which the refrigerant is guided to the second connection pipe via the switching valve while bypassing the outdoor-unit-side heat exchanger, so that the refrigerant is guided in accordance with operation modes including a cooling operation mode, a heating operation mode, a cooling main operation mode, and a heating main operation mode, - wherein the relay unit includes a first gas-liquid separating device that is connected to an intervening portion of the second connection pipe, a plurality of switching units (104: 12a, 13a; 12b, 13b; 12c, 13c) that individually connect the indoor units to one of the first connection pipe and the second connection pipe selectively, a first bypass pipe that connects the first gas-liquid separating device to each of the indoor units, a second bypass pipe that connects the first connection pipe to the first bypass pipe, a third flow control device provided to the first bypass pipe, and a second flow control device provided to the second bypass pipe, and wherein the multi-room air-conditioning apparatus is characterized by further comprising: - a second gas-liquid separating device provided between the outdoor unit and the relay unit and connected to the first connection pipe; - a gas-side outlet pipe that allows a gas refrigerant generated by gas-liquid separation performed by the second gas-liquid separating device to bypass the outdoor-unit-side heat exchanger and to flow into a refrigerant suction port of the compressor; and - a liquid-side outlet pipe that bypasses a liquid refrigerant generated by the gas-liquid separation performed by the second gas-liquid separating device to flow into the refrigerant suction port of the compressor via the outdoor-unit-side heat exchanger. - a second gas-liquid separating device provided between the outdoor unit and the relay unit and connected to the first connection pipe; - a gas-side outlet pipe that allows a gas refrigerant generated by gas-liquid separation performed by the second gas-liquid separating device to bypass the outdoor-unit-side heat exchanger and to flow into a refrigerant suction port of the compressor; and - a liquid-side outlet pipe that bypasses a liquid refrigerant generated by the gas-liquid separation performed by the second gas-liquid separating device to flow into the refrigerant suction port of the compressor via the outdoor-unit-side heat exchanger.