Provided are: a prepolymer which is capable of forming a non-linear optical material that has excellent non-linear optical effect, heat resistance, withstand voltage and transparency; a curable material which contains the prepolymer; a coating composition which contains the curable material and a solvent; a non-linear optical material which is obtained by curing the curable material; an optical waveguide which uses the non-linear optical material; and a light control device which is provided with the optical waveguide. The present invention uses a prepolymer having a crosslinkable functional group, which is obtained by reacting one or more compounds (X) that are selected from the group consisting of compounds (X1), compounds (X2) and compounds (X3), a compound (Y) that is represented by formula (Y), a compound (Z) that has three or more phenolic hydroxyl groups, and an organic compound (B) that exerts a non-linear optical effect and has a reactive group.