Abstract: A method includes separating at least 70% by volume of air in a double rectifier into oxygen, nitrogen gas and a gaseous argon fraction containing not more than 0.5% by volume of nitrogen. The latter is liquefied and fed into a rectifying column at a pressure exceeding a condensing pressure of the argon-nitrogen fraction by a value of from 0.01 to 0.06 MPa. A part of nitrogen gas is divided into two flows, a first of which is fed into the double rectifier and a second in an amount of not more than 40% by volume is sent into an evaporator of the rectifying column to deliver heat. The second flow of nitrogen may be changed by a part of the air being processed to be sent to said evaporator in an amount not in excess of 30% by volume.