To obtain a reactive derivative high in reactive rate, and so even without using catalyst, with little unreacted reactant and useful as cosmetic material by reacting a polysaccharide derivative contg. carboxyl group and soluble in an org. solvent with an epoxy silicone macromer having an alicyclic group on its one end.

As an epoxy silicone macromer having an alicyclic group on its one end, a compd. represented by the formula is used. In the formula, R1-R5 are each substituted or non-substituted 1-10C one valent hydrocarbons, and (n) is 3-20.0. A polysaccharide derivative is dissolved in an org. solvent such as a ketone like acetone, cyclohexanone, or the like, an ether or ester like dioxane, Butyl Cellosolve acetate, or the like, and a silicone macromer is added in an amount not higher than the carboxyl group equivalent and reacted for several hours with heating at 60-200°C under stirring. For the polysaccharide derivative, hydroxypropylmethylcellulose phthalate, and hydroxypropylmethylcellulose acetate succinate are pref.