A first driving force transmission part is disposed between an attachment part turning transmission shaft and a tool attachment part. The first driving force transmission part transmits rotary driving force from a side of the attachment part turning transmission shaft to the side of the first turning driving force transmission shaft, and includes a groove, a tenon shaped protrusion, and protrusions. The groove is formed on a tip of a slide shaft of the attachment part turning transmission shaft. The tenon shaped protrusion is formed in the first turning driving force transmission shaft and detachably engages with the groove. The protrusions once releases an engaging posture by pressing the groove that is biased to the engaging posture in an disengaging state when the tool is in the middle of the movement to a predetermined position.