PURPOSE: To automatically clear a display of a maximum value of a detected torque and a report of judged result of a normal area in an optionally set time and to detect a correct torque efficiently.

CONSTITUTION: The apparatus is provided with a clearing means for automatically clearing the maximum value of a detected torque displayed on a display 15 and the judged result of a normal area informed by informing means 16, 17 after an optionally set time has passed, and returning the apparatus to the state before the maximum value of the detected torque is judged. A timer 14 of the clearing means starts to measure a time from the time when a torque detected by a torque-detecting circuit 11 decreased to be smaller than a threshold value after the torque become larger than the threshold value in time sequence to the time when the clearing mean clears.