PURPOSE: To prevent a screw part from being easily detached from a tool, by making a screw part reach a target position in the state of being firmly held by the tip of an outer shaft, and performing the fastening with a rotation force being given to the screw part with the advance of an inner shaft.

CONSTITUTION: A tool main body 5 is composed of a hollow outer shaft 7 and an inner shaft 8 inserted into the internal part thereof in a freely retreatable and rotatable state, a holding part 9 provided at the tip of the outer shaft 7 can receive a hexagonal bolt head with the hexagonal hole 10 of the inside of the tip and an engaging part 12 with the screw part s provided at the tip of the inner shaft 8. When the head 2 of the bolt is fitted into the hexagonalhole 10, the holding power by a magnet 11 acts on the whole outer periphery of the head 2. When the bolt is pressed to the end of a screw hole by inserting it into a narrow place in this state, the outer shaft is stopped, only the inner shaft 8 is advanced and the rotation power can be transmitted to the bolt with the engaging part 12 being conformed to the hollow of the head 2 by turning a grip 6.