PURPOSE: To regenerate an anion exchange resin whose perrhenate ion adsorbing ability has been reduced by adsorption of a thiocyanato complex so that the resin can adsorb perrhenate ions.

CONSTITUTION: An anion exchange resin with an adsorbed thiocyanato complex of rhenium and molybdenum is brought into contact with an aq. soln. of an oxidizing agent which oxidizes the complex but does not deteriorate the resin and then the resin is brought into contact with an aq. alkali soln. At the time of the former contact, an aq. phosphoric acid soln. is allowed to coexist with the resin. After oxidation treatment, the resin is brought into contact with an aq. thiocyanate soln. Hypochlorous acid is used as the oxidizing agent.