PURPOSE: To perform drying, prevented from the occurrence of breakage, without forming a slit liner by a method wherein the temperature of the inside of a raw wood is increased to a specified value by using microwave energy and after the internal pressure of the wood is increased, a raw log is inputted in a hot blast drying chamber to effect drying processing.

CONSTITUTION: In prior to drying, wood is first inputted in a cylindrical microwave energy providing device. By irradiating the wood with microwave energy for a given time, the temperature of the interior of a raw wood is increased to approximate 55-100°C and the internal pressure of the wood is increased. Secondly, the wood is inputted in a drying chamber controllable of temperature and humidity and performs drying of the wood in a way to vaporize the moisture content of the wood through the butt end of the raw wood. Since drying prevented from the occurrence of breakage is executed without forming a slit liner in the wood, this drying method causes reduction of the number of processing processes, improvement of an yield, and the increase of a strength.