To manufacture a wall panel having various kinds of patterns by one mold by sticking a decorative sheet capable of seeing the pattern through a transparent plastic on the surface of a reinforced plastic base board.

A fiber reinforced plastic-made baseboard 2 is manufactured by projecting horizontal ribs 4, 5 on the rear face in the form of a lattice. A transparent or translucent plastic sheet 7 printing a pattern 9 on the rear face is stuck on a base material 6 by an adhesive 8 to form a decorative sheet 3. The decorative sheet 3 is stuck by an adhesive 10 over the outer face of the rib 4b of the end of the baseboard 2 so as not to be peeled on the butting part of adjacent wall panels 1 to manufacture the wall panel 1. Since a pattern 9 printed on the plastic sheet 7 is seen through, the wall panel 1 having a number of the patterns 9 can be manufactured by one kind of molds by preparing the plastic sheet 7 different in the pattern, so that a manufacturing cost can be reduced.