The invention relates to a numerically controlled lathe spindle drilling device, and belongs to drilling devices. The numerically controlled lathe spindle drilling device comprises a numerically controlled lathe, a clamp, a supporting sleeve, a pull pipe, a mandrel, a ball screw pair, an improved servo motor, a liquid flow device and a drilling taper shank combined cutter. According to the numerically controlled lathe spindle drilling device, a deep groove oilless combined ball bearing is arranged, so that the assembling precision and strength of the mandrel are improved, moreover, the mandrelis not limited by high-speed rotation of a machine tool spindle in a bearing hole, the axial reciprocating motion is free, the friction is reduced, the cutting stability of the cutter is improved, acutting fluid of the drilling device enters a cutting area through a liquid conveying hole inside the drilling device, so that the cutter and a workpiece are cooled, the cutting deformation is reduced, a built-up edge is prevented from being generated, the service life of the cutter is prolonged, and the product quality is improved; the drilling device has the advantages that the workpiece is clamped once, the two ends of the workpiece can be machined at the same time, multiple passes of working procedures are completed, the process can be optimized, the process flow can be shortened, the production efficiency can be improved, and the labor intensity of workers can be reduced.