To improve positioning accuracy including a restriction on a track up to installation of automobile parts in the assembly of the automobile parts using a power assisting device.

The tool 1 for the power assisting device is mounted in the power assisting device used when the automobile parts are positioned and assembled to a vehicle body. It includes a tool body 3 having a mounting part 3b for the power assisting device and supporting automobile parts, a sliding guide pin 5 supported by the tool body 3 and inserted in a guide hole opened on the vehicle body side, and a driving means 6 moving the sliding guide pin 5 back and forth.