PURPOSE: To cause resin to be uniformly cured, while even the fine gaps of hydrophilic resin-wooden material is impregnated with resin by a method in which after the wooden material has been impregnated with the condensation polymeric resin-aqueous solution to which chloral hydrate is added, radiation beam is radiated thereon.

CONSTITUTION: When the aqueous solution of the condensation polymeric synthetic resin to which chloral hydrate is added, is injected into wooden material by using injection means, even the inner part of the fine gaps of wooden cell is uniformly impregnated with resin-aqueous solution due to its hydrophilic nature. Then when radiation beam is radiated thereon, the chloral hydrate is decomposed by the radiation beam, and trichlor acetic acid is generated. The trichlor acetic acid becomes polymeric initiator, whereby the radiation beam-condensation polymeric reaction of the condensation polymeric resin- aqueous solution is carried out, and the resin is uniformly cured in the wooden material.