PURPOSE:To provide the titled compsn. which gives a coating film having excellent appearance and adhesion on olefin resin moldings, by dissolving a resin contg. a specified acid radical in an org. solvent. CONSTITUTION:0.05-10wt% alpha,beta-unsaturated carboxylic acid (anhydride) (a), e.g. maleic acid (anhydride), is grafted onto a styrene/butadiene/styrene block copolymer or a hydrogenated product thereof (b) to obtain a resin (A) contg. an acid radical which is a graft polymer contg. 10 -10 gram equivalents of COOH groups derived from component (a) per g of the resulting polymer. 5-50wt% (on a resin basis) component A is dissolved in 95-50wt% org. solvent (e.g. toluene) capable of dissolving component A to obtain the titled compsn. The compsn. is applied to the surface of an olefin resin molding in such a quantity as to give a coating film of 3-50mu in thickness. A paint such as urethane paint is then applied thereto.