To provide an air resupply tool for forcibly supplying air into soil around a tree without using a power source.

The air resupply tool for activating the tree is to be embedded in a ground around the tree. The air resupply tool comprises a cylinder to be embedded in the ground at a preset depth with an air supply pipe having a number of holes in the lower part being protruded from a bottom wall and the upper end being open and a piston inserted movably up and down into the opening end of the cylinder with the upper part being protruded and adapted to be energized upward by a spring stored in a cylinder chamber formed between the bottom wall thereof and the bottom wall of the cylinder.