PURPOSE: To selectively separate high-purity Y from an acid liquor containing Y and rate earths with small amounts of chemicals by simple equipment, by combining a stage in which Y and light rare earths are made high-purity by using a carboxylic acid-type extractant with a stage in which Y is subjected to high-purity separation by using an acidic phosphoric extractant.

CONSTITUTION: Y and light rare earths are made high-purity in the primary stage in which an acid liquor containing Y and rare earths is brought into countercurrent contact with a solution to which 50W70mol% of alkali, based on the total molar number of carboxylic acid and rare earth elements, is added. Then Y is subjected to high-purity separation from high-purity Y and light rare earths in the secondary stage in which the acid liquor recovered from the above stage is brought into countercurrent contact with an acidic phosphoric ester-type extractant. These two stages are not in particular order. According to this method, treatments with solutions of low acidities suffice, so that amounts of chemicals to be used, such as neutralizers, etc., can be minimized.