To provide a wooden foamed hardboard which dose not generate dioxins harmful to a human body and a component causing a sick house syndrome in jointing, has effects of keeping warmth, heat insulation, preservation of a scent and the like, is light in weight and shows good workability.

The wooden foamed hardboard utilized for a building material utilizes adhesive force exhibited by lignin and tannin contained in a liquid mixture of a prepolymer of a lignocellulose as a major component of timber and a foaming accelerator isocyante during foaming in case of bonding a foamed hardboard 1 and a natural board 2 without using an adhesive agent.