To provide a wooden underground mine-timbering for a transplanted tree disappearing with the lapse of time and allowing natural expansion of plant roots without giving a burden to the environment.

This wooden underground mine-timbering has wooden crossarms 5 horizontally crossing each other to become a buried state on the bottom of a plant hole after transplantation, wooden taking pressure boards 6 each fixed to the end of the crossarm and having a horizontal surface, and seizing tools 7 for lashing a rope 3 to be wound around a root ball 2 to the crossarm 5. A thrusting spear 8 thrusting the placed root ball 2 into from a lower part is built if necessary on the cross part of the crossarm 5. In addition, a wooden stand frame 9 to place the root ball 2 on is also attached to the cross part of the crossarm 5. It is possible to eliminate work in the plant hole for lashing the root ball and sufficiently tie the root ball to a stand with manpower above ground. There is no movable part advancing or retreating and the initial stability of the stand is high, thus the posture of a tree is retained from the underground without destroying the appearance of the tree.