[en] When adsorbed on a specially functioned fiber comprising an ion exchanger having a cation-exchange group, produced by grafting copolymerization with the radiation of Co⁶⁰-γ ray, rare earth metals like Sm, Gd can be eluted with an aqueous solution of a chelating agent in order, resulting in a successfull separation in rare earth metals. The exchange characteristics of the cation-exchange fiber have been determined and the influence of technological conditions in separation, such as Ph value, column ratio, linear velocity of eluting agent, concentration of eluting agent, concentration of weak acid and temperature, on the separation efficiency of Sm from Gd have been studied. It is confirmed that this separation process is better than the previous ones. (author) 35 figs., 8 tabs., 4 refs