A method for purifying a biologically active substance from a solution mixture containing impurities and the biologically active substance, in which an ion exchange chromatography carrier comprising a matrix and a copolymer containing at least N-isopropylacrylamide as a monomer unit and immobilized to a surface of the matrix is used, and the solution mixture is allowed to flow through a container storing the carrier at a uniform temperature, thereby recovering the biologically active substance.