PURPOSE: To correct warpage condition permanently, and make any warpage invisible thereon as being laid on a floor by fixing integrally a net material stitched by a low extensible fibre between a warpage corrected wooden plate and backing sheet material to be plated on the back surface of the wooden plate together with the sheet material.

CONSTITUTION: Narrow split wooden plates 14 are aligned on the smooth work surface 15 of a mold frame 15 in the form facing the back surface upwards, and mutual wooden plates 14 are brought into close contact with one another by applying a pressure from the side thereof, and an adhesive agent is applied on the back surface thereafter. A net material stitched by a low extensible fiber 16 is put on the place to undergo an adhesive agent treatment, and a soft backing sheet material 17 is placed further thereon. In the next place, while the warpages of respective wooden plates 14 are corrected by applying a pressure from the upper direction, the net material 16 is integrally fixed with the backing sheet material 17. The net material 16 is a type of one stitched by the use of, for example, glass fiber yarn in its warp, and nylon in its weft, and as being fixed such that the warp is placed in the longitudinal direction of the wooden plate 14, the regeneration of warpage can be prevented by the inextensible property, thereby surely maintaining the corrected conditions permanently.