Abstract: The present invention is intended to artificially break pit membranes in cell membranes of cells constituting wood and then to readily attain dryness of the wood. In view of the fact that one pit or the other pit of pits in the form of a pair is blocked with the torus 1 in felled wood to cause poor removal of water in cells, it is intended to prevent the blockage of the pit membrane, i.e., to break the pit membrane per se, thereby facilitating easy escapement of water in cells after the breaking. In the present invention, wood fuel is burned, and subject wood is allowed to stand in a treatment chamber filled with smoky wood gas generated by the combustion for a predetermined period of time, to expose the subject wood to far-infrared radiation and components contained in the wood gas.