To provide a tooth mobility measuring instrument which can measure the mobility of a tooth without making a patient feel uncomfortable.

This tooth mobility measuring instrument 10, suitable for measuring the mobility of front teeth, applies a prescribed volume of direct current pulse voltage to a tooth 1 by hooking a hook 11 on the tooth 1 and inserting a lead wire 15 into an electromagnetic converter 13, and moves a drive shaft 12 in both ways in the arrowed directions A (the movement in the return direction is made by return spring). When the mobility of the tooth 1 is large, the drive shaft 12 is widely displaced in the arrowed directions A; and when the mobility of the tooth 1 is small, the displacement of the drive shaft 12 in the arrowed direction A is small. So the displacement of the drive shaft 12 in the arrowed direction A is detected by a displacement sensor 14, and is displayed on a display monitor, etc., through a lead wire 16.