Abstract: A furnace is set to the floor section where wastes such as wood chips, scrapped wood, or wood pieces are put, flammable wastes such as planer chips, plane chips, bark, branches and leaves, or waste paper are arranged as an ignition material so as to cover the upper and lower sides of the wastes. Several resistant steel lids are lain one upon another on the upper side of the furnace so that heat and smoke can pass through the gap between the lids. The ignition material is ignited and inside combustion material is incompletely burned keeping the central portion of green-wood stacked on the upper side in a range of 75 to 80.degree. C. The green-wood is smoking-seasoned at a low temperature by supplying smoke and hot air to the wood and the stacked wood is seasoned at a low temperature by convection blowers arranged at various positions in the indoor temperature adjusting damper and the room.