Air extractor

The invention provides an air extractor capable of efficiently exhausting air. The present invention is provided with: a gas extraction pipe (71) that is connected to a condenser (12) and extracts a mixed gas containing a refrigerant gas and air from the condenser (12); a separation membrane (23b) which is provided in the air extraction pipe (71) and which separates air from the mixed gas extracted by the air extraction pipe (71) by means of a pressure difference; an exhaust pipe (81) that guides to the outside a gas containing the air separated by the separation membrane (23b); a first valve (24) provided in the exhaust pipe (81); a vacuum pump (27) that is provided downstream of the first valve (24) in the exhaust pipe (81) and that discharges gas within the exhaust pipe (81) to the outside; and a control unit (50) that operates the vacuum pump (27), opens the first valve (24), and, when it is detected that a prescribed amount of air has passed through the separation membrane (23b), closes the first valve (