PURPOSE: To rapidly infiltrate an enough amount of treating liquid in the depth of stock wood with a simple device by a method wherein one end side part of the stock wood is immersed in the treating liquid and, under the above- mentioned condition, the solvent of the treating liquid is forcible evaporated from the other end side part of the stock wood.

CONSTITUTION: The root side butt end 1a of green wood 1 is immersed in treating liquid 3 in a liquid tank 2 while its opposite side butt end 1b is protruded beyond the treating liquid 3. On the other hand, a pair of aluminum electrodes 5 and 5, which are coated to the other butt end 1b, is energized from a high frequency power source so as to heat the butt end 1b in order to forcibly evaporate solvent.