To provide a technology for dimensional stabilization of woody plates which provides high productivity and cost advantage.

In a woody plate, a heat-compacted layer impregnated with a glyoxal resin is formed at least on one side of a woody substrate. By the heat compaction of the surface on which the glyoxal resin is applied, the impregnation and adhesion of the resin can be achieved easily. By the impregnation carried out under high pressure heat compaction of the substrate surface, the surface layer increases its density and fixed firmly so that a woody plate is obtained in which not only the dimensional stability but the surface strength and the flexural strength are improved remarkably.