Abstract: A synthetic resin molding for the use of automotive vehicles are of the type in that an elongated molding product is cut into a predetermined length and mounted to a body, a window frame, a bumper or the like of automotive vehicles. The molding is constituted as such that a plurality of core yarns of glass fiber are applied to the interior of a body of the molding in parallel relation along the longitudinal direction by continuously feeding a plurality of yarns of glass fiber into a mold in the body of the molding. Therefore, the thermal contraction can be greatly minimized.