Abstract: A method for manufacturing a modified wood prepares a natural wood material containing more than a predetermined amount of a solvent for dissolving two different compounds which chemically react with each other to form an insoluble compound, provides a layer of each of the different compounds inside each of two opposing surfaces of the wood material, causes the different compounds to chemically react with each other within the wood material and fixes the formed insoluble compound in the wood material, whereby the fixation amount of the insoluble compound in the wood can be effectively increased.

Abstract: In a method of treating a raw wood material with a formaldehyde polymer in the presence of sulfur dioxide at a reaction temperature within a reaction vessel to obtain a modified wood material, sulfur dioxide is supplied into the reaction vessel when a gas pressure of the formaldehyde polymer within the reaction vessel is 4.00.times.10.sup.4 Pa or more. In addition, a concentration of the formaldehyde polymer is in a range of 30 to 350 mol/m.sup.3 of formaldehyde monomer, and a molar ratio of the formaldehyde polymer to sulfur dioxide is in a range of 10 to 350. As the formaldehyde polymer, for example, trioxane, tetraoxane, or paraformaldehyde is used. The modified wood material manufactured by the method including the above conditions shows excellent dimensional stability while a discoloration thereof is effectively prevented. Therefore, the modified wood material is particularly fit to use for an interior furniture, musical instrument and a bath tub, etc.