A method of adsorbing a substance such as an optically active substance, comprising contacting a solution of the substance in a solvent with an adsorbent, consisting of a cross-linked, polymer comprising an optically active, synthetic.poly(amino acid)represent by the general formula (I):wherein R stands for an organic group, R' stands for hydrogen or an alkyl group and n is an integer of at least 5, which may be protected at a terminal amino group and a carrier polymer supporting said synthetic poly(amino acid) thereon, said carrier polymer having affinity for said solvent.The adsorbing is especially useful for optical resolution of racemic mixtures.