PURPOSE: To positively and easily penetrate an impregnating solution into a log of any shape in a short time with respect to a method for impregnating wood, such as a log, with a solution of a preservative, a mothproofing agent, an antiflaming agent, or the like.

CONSTITUTION: As an operation of a first stage, a sealing material 9 is formed by curing and securely fixing a curable sealing resin liquid, such a silicone rubber, to the outer periphery of the lower end of a log 4. As an operation of a second stage, the butt end is cut or ground, and the log is set in a cylindrical impregnating liquid container 7 as shown by a figure. Impregnating liquid 12, such as treating liquid, pressurized by a pressurizing pump 10 is supplied into the cylindrical impregnating liquid container 7 and pressurized, thereby being penetrated into the log under pressure from the lower butt end of the log through gaps of a grating mount 11. At this time, the leakage of the impregnating liquid is prevented by bringing the outer peripheral surface of the log into pressure contact with the inner surface of the cylindrical container by the sealing material 9.