The present invention provides a machine tool with a spindle chuck replacing mechanism which is simply configured to enable a reduction in time for work replacement without the need to sense the rotation speed of a spindle chuck or the like. The machine tool includes a pre-rotation-transmission mechanism 7 transmits rotation of a spindle motor 4, via a path different from a chuck coupling portion 3a of a spindle 3, to a spindle chuck 5 placed in a processing position P1 and not coupled the chuck coupling portion 3a. The pre-rotation-transmission mechanism 7 makes a difference in rotation speed between the spindle chuck 5 and the spindle 3. The pre-rotation-transmission mechanism 7 has a speed difference absorbing mechanism 23 that absorbs the difference in rotation speed with the spindle chuck 5 coupled to the chuck coupling portion 3a.