Abstract: A replaceable tool is comprised of a tool holder forming a hole providing an engageable ditch on the insert end of the shank, a fitted hole for detachably fitting the shank of this tool holder therein and a sleeve providing a plurality of locking balls to be engaged and removed from the fitted ditch of the tool holder in the fitted hole. In the interior of the fitted hole of the sleeve, the locking balls are pressed on the engageable ditch and the draw collar for applying attraction in the axial direction of the sleeve is slidably provided. When the shank of the tool holder is fitted in the fitted hole of the sleeve, the head portion end of the tool holder is designed to be pressed on the end flange portion of the fitted hole of the sleeve, and when the draw collar is pulled in the axial direction of the sleeve, the shank portion is expanded through locking balls so as to be pressed on the inner wall surface of the fitted hole of the sleeve.