An abnormal state detecting apparatus of a machine tool having a servomotor. The apparatus is provided with a device for detecting an abnormal acceleration and an abnormal torque of the servomotor and a device for detecting an abnormal operation state of the servomotor from the directions of the detected acceleration and torque. When the torque, acceleration and operation state are all abnormal, the machine tool is judged to be in an abnormal state and the servomotor is controlled, thereby protecting the machine tool from an impact in an abnormal operation state.