Abstract: A keyless drill chuck includes a raising-and-lowering member which moves back and forth with reference to a shaft in order to secure a rear portion of the cutting tool, and jaws which grip the cutting tool in association with the movement of the raising-and-lowering member toward the jaws while the internal diameter of a circle defined by the jaws. The rear portion of the cutting tool is automatically gripped without the use of a chuck handle by means of a machining resistance transmitted to the jaws from the cutting tool and of the movement of the raising-and-lowering member caused by torsional torque transmitted to a shaft. A V-shaped recess is formed in the end of the raising-and-lowering member facing the jaws, so that the rear portion of the cutting tool can be removable, yet attached to the V-shaped recess.