Examinations were made on Kitagawa's method for preparation of canavanin from Canavalia ensiformis and a method was devised for the use of ion-exchange resin to prevent occlusion of deaminocanavanin, which is responsible for lowering the purity and biological activity of canavanin, and to simplify the procedure. This new method was found to give the free-form canavanin of high purity, easily and in a good yield, directly from its flavianate.