A locking drill chuck comprises a chuck body, a plurality of jaws, a nut, a front sleeve, and a rear sleeve, wherein the chuck body has an axial hole at its rear end for engaging with a driving shaft of a driving means, and the rear sleeve close fits with the outer circumference of the rear end of the chuck body, the jaws are separately fitted in a plurality of corresponding inclined holes equally departed away from each other in the chuck body, the nut engages with the jaws, the locking drill chuck further comprises a locking sleeve provided between the front sleeve and the rear sleeve, and connected with the front sleeve; and a locking assembly provided between the nut and a stop surface of the chuck body, the locking assembly includes rolling members and a locking plate, wherein the locking plate connects with the locking sleeve, and has a plurality of eccentric grooves in an end plane thereof, the rolling members is received in the eccentric grooves, the stop surface of the chuck body includes a conical portion and a plane portion. The locking drill chuck in accordance with the present invention is convenient for machining process, with lower product cost, and is more steady and reliable in operating.