An air-conditioning apparatus configured to supply conditioned air to a room through an air supply duct by operating an air-sending device , the air-conditioning apparatus comprising: a housing having an outside air port , an air supply port , a return air port , and an exhaust port , the outside air port adapted for taking outside air into the housing , the air supply port adapted for supplying the outside air taken into the housing from the outside air port to the room , the air supply duct being connected to the air supply port , the return air port adapted for taking air into the housing from the room , the exhaust port adapted for exhausting the air taken into the housing from the return air port to an outside; an outside air passage formed in the housing configured to make the outside air port and the air supply port communicate with each other; an exhaust air passage formed in the housing in a separated manner from the outside air passage configured to make the return air port and the exhaust port communicate with each other; an indoor heat exchanger disposed in the outside air passage , comprising a refrigerant adapted for flowing through the indoor heat exchanger ; the air-sending device disposed in the outside air passage , and configured to generate an air flow directed toward the room from the outside air port via the air supply port and the air supply duct during operation; and an air supply damper configured to open and close the air supply port , the air supply damper being configured to be open during the operation of the air-sending device and being configured to be closed during a stop of the air-sending device the air-conditioning apparatus being characterised by comprising an open port formed in the housing configured to cause the outside air passage to be open to the outside; and an open port damper configured to open and close the open port , wherein the open port damper is configured to be closed during the operation of the air-sending device , and is configured to be open during the stop of the air-sending device . a housing having an outside air port , an air supply port , a return air port , and an exhaust port , the outside air port adapted for taking outside air into the housing , the air supply port adapted for supplying the outside air taken into the housing from the outside air port to the room , the air supply duct being connected to the air supply port , the return air port adapted for taking air into the housing from the room , the exhaust port adapted for exhausting the air taken into the housing from the return air port to an outside; an outside air passage formed in the housing configured to make the outside air port and the air supply port communicate with each other; an exhaust air passage formed in the housing in a separated manner from the outside air passage configured to make the return air port and the exhaust port communicate with each other; an indoor heat exchanger disposed in the outside air passage , comprising a refrigerant adapted for flowing through the indoor heat exchanger ; the air-sending device disposed in the outside air passage , and configured to generate an air flow directed toward the room from the outside air port via the air supply port and the air supply duct during operation; and an air supply damper configured to open and close the air supply port , the air supply damper being configured to be open during the operation of the air-sending device and being configured to be closed during a stop of the air-sending device the air-conditioning apparatus being characterised by comprising an open port formed in the housing configured to cause the outside air passage to be open to the outside; and an open port damper configured to open and close the open port , wherein the open port damper is configured to be closed during the operation of the air-sending device , and is configured to be open during the stop of the air-sending device . <EOS>