<p>A CNC tapping machine includes a spindle (14) to which a tap (T) is attached and a spindle motor (15) for rotating the spindle (14). The load torque acting on the spindle motor (15) that is detected when performing a tapping procedure without a workpiece (W) is stored in a memory (31) as referential torque data. During a tapping procedure, a detection device (25) detects the load torque acting on the spindle motor (15). A computer (23) computes the difference between the load torque detected by the detection device (25) and the referential load torque and uses the difference as the cutting load acting on the tap (T). As a result, the cutting load torque acting on the tap (T) is accurately detected.</p>
