The present invention provides a cation-exchange chromatographic support, comprising a membrane matrix and a copolymer immobilized on the surface of the membrane matrix, wherein the copolymer comprises a (meth)acrylamide-based compound and/or a (meth)acrylate-based compound as monomer units, and the support has one or more species of cation-exchange groups including at least a weak cation-exchange group at a density higher than 30 mmol/L per volume of the support.