PURPOSE: To prevent adhesion of a chemical agent to a cutting blade and generation of burn in a cut surface of lumber, by cooling a cutting processing blade and a part of the lumber to be cutting-processed with a low-temperature refrigerant such as liquid nitrogen.

CONSTITUTION: A blade 1 and a cut part of impregnation-treated lumber 2 with a chemical agent are covered with a hood 3 provided with a discharge duct 3a, a liquid nitrogen is introduced into the hood 3 from a Dewar-shaped liquid nitrogen cylinder 4 through a reducing valve 5 and regulating solenoid valve 6 and the same is blown against the blade 1 and the cut part of the impregnation-treated lumber 2. The solenoid valve 6 is connected with a temperature control device 8 actuating by receiving a signal of a thermistor temperature sensor 7 provided within the duct 3a. With this construction, if the thermistor temperature sensor 7 is established at a fixed temperature, the liquid nitrogen is regulated and blown off. The blade 1 and cut part are held at almost a fixed low-temperature and adhesion of the chemical agent to the blade 1 and generation of burn in a mold 2a are eliminated.