A control apparatus of a machine tool including a feed axis, which is driven by a feed axis motor, includes a load torque estimation unit configured to estimate a load torque acting on a spindle motor, based on a torque command to the spindle motor which drives a spindle axis of the machine tool, and a speed of the spindle motor; and a speed control unit configured to control a speed of a feed axis motor such that the load torque estimated by the load torque estimation unit follows a prescribed load torque target value.

A control apparatus of a machine tool including a feed axis, which is driven by a feed axis motor, includes a load torque estimation unit configured to estimate a load torque acting on a spindle motor, based on a torque command to the spindle motor which drives a spindle axis of the machine tool, and a speed of the spindle motor; and a speed control unit configured to control a speed of a feed axis motor such that the load torque estimated by the load torque estimation unit follows a prescribed load torque target value.