The present invention relates to a method for purifying an aqueous solution of fermentation alcohol to give anhydrous alcohol, wherein a mash column is controlled such a manner that an alcohol concentration of an alcohol/water mixed vapor distilled from a mash column is less than 50% by weight and a reflux amount of a condensate to a distillation column is controlled such a manner that an alcohol concentration of an alcohol/water mixed vapor that is distilled from the distillation column is 65 to 85% by weight. According to the present method, the purification for obtaining an anhydrous alcohol from an aqueous solution of a fermentation alcohol with the use of a mash column, a distillation column, an evaporator and a membrane separator can be more conveniently carried out with an extremely high energy efficiency as the whole process.