PURPOSE: To impregnate material woods with a chemical efficiently without losing time by sending the material woods to a chemical impregnating tank and a dewatering tank sequentially in series, carrying out dewatering processing and chemical impregnating operation in the chemical impregnating tank, and reducing the pressure in the dewatering tank so as to remove extra adhering chemical.

CONSTITUTION: A material wood W is sent onto a lifting conveyor 63 of a first lift 6 through a roller conveyor 2 and a pressing rod 68b is made to descend so as to press the wood W. Then, the conveyor 63 is made to descend together with a cover 66, the wood W is dipped into a chemical impregnating tank 3, and an upper opening is closed by the cover 66. Next, a vacuum pump 32 and a pressure pump 32' are driven properly. After chemical impregnating processing is performed, the conveyor 63 is lifted and the pressing rod 68b is lifted. The wood W1 is transferred to a lifting conveyor 73 of a second lift 7, the conveyor 73 is made to descend together with a cover 76, and the wood W1 is mounted in a dewatering tank 4. After the pressure in the tank 4 is reduced and the adhered chemical is removed, the conveyor 73 is lifted and a dewatered wood W2 is transferred to a roller conveyor 5.