PURPOSE: To provide a self-supporting fixing tool and a fixing method for a tree capable of avoiding the damage of buried facilities under the ground and effectively assisting the self-support of the tree in the planting of roadside trees.

CONSTITUTION: A resistance plate 7 composed of three planes formed by bending a plate to form a U-shaped cross section is fixed to an angle to enable the development of large resistance to the earth pressure even if the resistance plate 7 has short length. The damage on buried facilities can be avoided by this structure. A root ball 11 is integrated with each fixing tool by a tightening band 12 fitted to a hook 6 and a fixing pin 4 to fix the angle and the root ball 11.