PURPOSE: To lower the cost of molds, and to effect the bending readily, by extruding and molding a planar synthetic resin plate having an insert of a thin metal sheet, and passing the resin plate through a group of heating and molding rolls the curvatures of the outer circumferential surfaces of which are progressively increased along the path of the extrusion.

CONSTITUTION: The thin metal sheet 1 is fed to a crosshead die 7 while a synthetic resin material is extruded by an extruder 3, so that the planar synthetic resin plate 2 with the thin metal sheet 1 inserted is obtained. The synthetic resin plate 2 is passed through the group of heating and molding rolls 4 that are arranged such that the curvatures of the outer circumferential surfaces of the rolls are successively increased in the direction of the extrusion of the resin. Thus the synthetic resin plate 2 is bent in such a way that the curvature is progressively increased. Accordingly, the cost of the molds can be lowered, and the bending and molding can be readily effected.