Abstract: Provided is a treefall preventing device capable of reliably preventing a planted tree from falling A treefall preventing device 1 is buried in soil such that roots 32 entwine the treefall preventing device 1 as a planted tree 30 grows, wherein the treefall preventing device 1 comprises three or more supporting parts 2 extending in parallel with each other and ring-like retaining bodies 4 supported by the supporting parts 2, and the retaining bodies 4 are secured so as to be placed at intervals along the supporting parts 2. The treefall preventing device 1 is disposed in the bottom part of a planting hole 12, secured by pile members 20, and then buried, and a tree 30 is planted above the buried treefall preventing device 1.