The invention discloses a quick replacing device for clamp bodies of a numerically-controlled machine tool. The quick replacing device comprises a numerically-controlled machine tool workbench, the clamp bodies and hydraulic cylinders, wherein inner conical holes are formed in the numerically-controlled machine tool workbench, through holes are formed in the parts, of the numerically-controlled machine tool workbench, below the inner conical holes, the diameters of the through holes are smaller than those of the lower bottom surfaces of the inner conical holes, and the through holes are communicated with the inner conical holes; a positioning table is arranged at the bottom of each clamp body, and each positioning table is provided with a cone matched with the corresponding inner conical hole; the hydraulic cylinders are arranged below the numerically-controlled machine tool workbench, and the pistons of the hydraulic cylinders are arranged inside the through holes and are matched with the through hoes in size; the tapers of the inner conical holes and cones all adopt Morse taper. After the structure is adopted, the quick replacing device is simple in structure and convenient to use and saves time and labor, the clamp bodies of the numerically-controlled machine tool can be quickly replaced, and the mounting accuracy of the clamp bodies is high.