This invention relates to an air separation method and apparatus for liquefying and separating feed air into oxygen and nitrogen by use of a single rectification column. The temperature of the feed air, which is liquefied, is reduced to the temperature necessary for the condensation and liquefaction of pure vaporous nitrogen inside the single rectification column and is used to condense and liquefy the pure vaporous nitrogen and vaporize the feed air. After the pressure of the feed air thus vaporized is raised to the pressure necessary for the condensation and liquefaction of the pure vaporous nitrogen inside the single rectification column, the vaporized feed air is introduced into the single rectification column so that pure gaseous nitrogen can be withdrawn from the top of the single rectification column, pure gaseous oxygen from a lower portion of the column and waste gas rich in nitrogen from an intermediate portion of the column. Thus, the present invention makes it possible to carry out air separation with a high rate of recovery of oxygen using a single rectification column.