Abstract: An electric power tool in one aspect of the present disclosure includes a motor, an output shaft, a drive circuit, a rotation controller, a calculator, and a deceleration controller. The output shaft is configured to attach a tool bit thereto, and be rotated by the motor. The rotation controller rotates the output shaft to thereby loosen a fastener from a fastened material. The calculator increases a determination value in accordance with a lapse of time from a first timing, and varies a rate of increase in the determination value in accordance with a speed parameter. The deceleration controller decelerates or stops the motor based on the determination value having reached a threshold value.