An electric power steering device includes a restricting portion that is provided on at least one of surfaces of a housing and a worm wheel, the surfaces facing each other. The restricting portion is configured to restrict movement of the worm wheel to maintain a meshing relationship between a worm and the worm wheel that allows torque transmission between the worm and the worm wheel, when fixing of the worm wheel to an output shaft of a power assist actuator in an axial direction of the output shaft is released and the worm wheel is moved in the axial direction.