To prevent an interlaminar release between a case edge base material and a decorative sheet by adhering a folding case edge material obtained by laminating the sheet on a surface to a adhered to be adhered by superposing both ends obtained by folding the case edge material obtained by laminating the sheet on the surface in a cylindrical state from the first in the state that the sheet is not laminated.

A decorative sheet 2 on which an woodgrain is printed is laminated on one side surface of a case edge base plate 1 made of a timber, plastic foam material, cardboard or the like. The sheet 2 is not laminated on an adherend 3 to be adhered by coating it with an adhesive of one end and superposing it. The part 3 is coated with a hot-melt or cyanoacrylate instantaneous adhesive agent, or an adhesive such as an emulsion bond or the like, superposed, press bonded and sandwiched until it is fixed by a press bonding plate from both surfaces. This bonding plate may be heated, for example, at 50 to 100°C to accelerate curing of the adhesive. Since no sheet 2 exists on the superposed adhered part, the case edge plates 1 can be rigidly adhered to one another.