To enhance strength and dimensional stability and enable an incineration treatment and biological decomposition treatment by impregnating a wooden raw material with an aqueous solution of a low molecular phenol resin and forming it at a specific temperature under high pressure after drying it.

A wooden raw material is impregnated with an aqueous solution of a low molecular phenol resin having concentration of 2-20wt.% and dried to form it at a temperature of 140-200°C under the high pressure of 500-1000kg/cm2. The concentration of the aqueous solution is preferably 5-15wt.%. As the wooden raw material, a wooden fiber, a wood power, a bamboo powder, waste oil palm, old news paper, kaoliang, bagasse, rice straw, and chaff can be used and even materials, which are usually abandoned, can be reutilized. When wooden fibers are used as a wooden raw material, it is preferable that the length of the fibers is 0.8-2.0mm and diameter thereof is 5-300μm.