<p>An electric power tool includes a motor (1); a speed reducer (2) for transferring a rotational power of the motor at a reduced speed; and a reduction ratio changing unit for changing a reduction ratio of the speed reducer. The speed reduction mechanism includes an axially slidable changeover member (7) and a gear member (5), the changeover member being engaged with or disengaged from the gear member depending on an axial slide position thereof. The reduction ratio changing unit includes a shift actuator (6) for axially sliding the changeover member, a driving state detector (60) for detecting a driving state of the motor, a slide position detector (61) for detecting a slide position of the changeover member and a controller (62) for driving the shift actuator and for changing a drive control of the shift actuator depending on detection results of the slide position detector unit (61) and the driving state detector unit, respectively.</p>
