PURPOSE: To promote hardening of an adhesive and to shorten a pressing time necessary for bonding by mixing a hardening promoter in order to promote hardening of the adhesive which is utilized for bonding a ligneous decorative veneer on the ligneous base material in the production stage of the ligneous decorative veneer.

CONSTITUTION: In the case of producing the ligneous building material by applying an adhesive to the lumber flakes 1 and making them to a block by clamping, molding and slicing the formed flitch 3 and bonding the obtained ligneous decorative veneer 5 on the ligneous base material 11 by the adhesive 12, a hardening promoter is mixed in order to promote hardening of the adhesive 12 which is utilized for bonding the ligneous decorative veneer on the ligneous base material 11 in the dyeing stage of the lumber flakes 1 in the production process of the ligneous decorative veneer 5. As the hardening promoter, for example when the adhesive 12 utilized for bonding the ligneous decorative veneer on the ligneous base material 11 is the urea-vinyl acetate based adhesive 12, an ammonium chloride soln. is utilized. Thereby hardening of the adhesive penetrated into the ligneous decorative veneer is promoted by the hardening promoter mixed therewith and therefore a pressing time can be shortened.