Abstract: In a chuck comprising a holding cylinder having a tapered outer circumferential surface and an objective tool or an adapter for holding such a tool inserted therein, and a clamping cylinder rotatably mounted at a predetermined distance from the outer circumferential surface of the holding cylinder, a number of needle rollers being arranged in a plurality of stages along the entire circumference of a gap between the two cylinders to extend along a direction at a predetermined inclined angle .alpha. with respect to the common axis of the cylinders, and the needle rollers rotating and revolving upon rotation of the clamping cylinder, thereby contracting and recoverying the holding cylinder, slits are formed in the holding cylinder to allow elasticity of the holding cylinder and to improve oil throwing performance and clamping force of the holding cylinder. The slits will not interfere with smooth rotation of the needle rollers.