To provide a positioning tool capable of simply and correctly adjusting the position of a sensor in the axial direction.

This positioning tool 1 is used for a device 17 provided with an immovable fixing member 18 and an axis 2 slidably is inserted through the fixing member 18. The positioning tool 1 comprises a body part 3 fastened onto the axis 2, and a sensor 4 supplemented with the body part 3 and detecting a positional relation of the fixing member 18 to the axis 2 in the axial direction through contact with the fixing member 18. A screw hole 16 extending in the axial direction is provided on the body part 3, to form a male screw 10a on the periphery of an outer case 10 of the sensor 4. By screwing the outer case 10 to the screw hole 16, the sensor 4 is installed to the body part 3 so as to be adjustable in the axial direction.