A method of producing a novel separating agent for separating enantiomeric isomers, characterized by including: a step of supporting an optically active polymer compound and a compound having an asymmetric structure of a molecular weight of 1,000 or less on a carrier using a solvent; a step of removing the solvent; and a step of removing the compound having the asymmetric structure of the molecular weight of 1,000 or less by washing.