PURPOSE: To reduce a power of selection time for selecting a bit by the rotation of a bit holder, to lock with a handle main body excepting election time and not to move to a bit storing room during the use, by providing a lock mechanism between the bit holder and handle main body as well as incorporating the bit holder into the handle main body.

CONSTITUTION: An operation grip 25 is turned in a positive direction from a reference position, the position of an operation pin 29 is retreated in the base part direction by a cam groove, one part 11, 13 of a holder part is retreated in the base part direction and the biting of biting parts 6, 6' is released. Thus, the lock of a handle main body 1 and bit holder 16 is released and a rotating 14 is made rotatable. Then, the rotating knob 14 is turned, the relative position of a bit storing room 16 and liaison window is changed and then the bit storing room 16 in which a bit to be used is stored and liaison window 26 are made coincident. Thereafter, the both 1 and 16 are locked again and this bit is offered for use.