To reduce the formaldehyde discharge amount to the specified amount or less and improve mothproofness and mildewproofness by adding borax or boric acid mothproofing and mildewproofing agents to a formalin bonding agent for a woody board.

As borax or boric acid used as a mothproofing agent or a mildewproofing agent is provided with the low solubility in water, a borax or boric acid reaction compound is used instead. The solubility of the reaction compound is approximately 25 %, and the reaction compound as a boric acid water solution of higher concentration is added into a bonding agent to prevent the lowering of the concentration of the bonding agent. First, a water solution of odorless urea resin bonding reaction compound is added and agitated sufficiently. The bonding agent is added to particle board surface layer chips and particle board inner layer chips respectively, at the ratio, for example, of 12% and 8% respectively as the resin solid contents. Chips are hot-pressed to manufacture a particle board. Thus a woody board of formaldehyde discharge amount of 1.5 mg/l or less is manufactured by adding borax or boric acid mothproofing and mildewproofing agents to a formalin bonding agent for the woody board by the arrangement.