A wood treatment apparatus for long-term treatment of wood has a cylindrical hollow body and a sleeve. The cylindrical hollow body has an inner end, during use located within the wood, an outer end, directed away from the inner end, an exit opening and an accommodating space accommodating a carrier material containing active wood-treatment substance. The sleeve is arranged around the cylindrical hollow body and, when the apparatus is not in use, closes the exit opening and, when the apparatus is used, frees the exit opening and brings the accommodating space into contact with the wood. The method provides driving the apparatus into the wood to position the exit opening near a site to be treated and displacing the sleeve to bring the accommodating space into contact with the wood, wherein the apparatus remains in the wood to allow the wood-treatment substance to be released pressureless into the wood.