Abstract: There is disclosed a chuck adapted to be attached to the spindle of a machine tool, for gripping an intended tool, comprising a chuck barrel adapted to grip an intended tool and having a conical outer peripheral surface and not having slots extending along the generating lines thereof, a clamp ring fitted over said chuck barrel, and a number of rollable bodies in the form of needle rollers interposed between said clamp ring and said chuck barrel and inclined at a fixed angle with respect to the generating lines, the arrangement being such that when said clamp ring is manipulated for rotation, said rollable bodies spirally revolve around the axis of the chuck barrel along the conical peripheral surface thereof while rotating around their own axes, thereby effecting the contraction and configurational restoration of the chuck barrel, said chuck being characterized in that a restraining ring is attached to the outer peripheral surface of said clamp ring and rollable bodies, particularly in the form of needle rol