The present invention provides an additive for a hair cosmetic preparation and a hair cosmetic preparation containing the additive that can give a supple feel to the finished hair. The additive for a hair cosmetic preparation contains a graft copolymer obtainable by graft-copolymerizing a cationic water-soluble monomer and a nonionic water-soluble monomer in an aqueous solution containing either one or both of a natural polymer and a natural polymer derivative that have an OH group.