The durability of a reduction mechanism is improved. An impact wrench includes a brushless motor, a sun gear rotatable by the brushless motor, a planetary gear meshing with the sun gear, an internal gear meshing with the planetary gear and having a first recess on an outer circumference, a gear case holding the internal gear and having a second recess on an inner circumference, a spindle holding the planetary gear, and a pin disposed in the first recess and in the second recess.