A cation exchange membrane carrying N-(8-quinolyl)-sulfonamide was prepared by attaching the chelating reagent to side chains of a polymer. The chelating reagent was known to have selectivity for CU2+ over Fe3+. Acrylic acid was also introduced to add a hydrophilic property. All compounds were identified by mp, elemental analyses, IR, H-1 NMR, C-13 NMR and GC-MS. The ratio of the chelation monomer to the acrylic acid was varied between 1:7 and 1:1. The molecular weight of the prepared polymer, determined by gel permeation chromatography, was between 5 X 10(5) and 10(7). The above polymer diluted with Me,SO was impregnated into a porous Teflon membrane and then the solvent was evaporated. The membrane had enough hydrophilicity even after the above operation. The membrane was sandwiched between 2 glass cells filled with a CU2+ and Fe3+ mixture solution at a pH of 2.0 (extraction side) and with 1 N sulfuric acid (stripping side), respectively. The apparent diffusion coefficient of Cu2+ through the present membrane was almost comparable or a little smaller than that of the commercial one, while that of Fe3+ was suppressed remarkably. Thus, the selectivity of Cu2+ over Fe3+ became 2.6, i.e., ca. double that of the commercial membrane.