A window regulator 1 comprising a drum housing 7. A polygonal hole 721 formed in the drum housing 7 has first to sixth recessed corners 721a–721f that correspond to each of the first to sixth corners 110a–110f in a polygonal section 110. An inside surface of a guide hole 722 has first to sixth inclined sections 722A–722F that guide a relevant corner to one of the recessed corners among the first to sixth recessed corners 72a–721f in the polygonal hole 721 by coming in contact with a corner of the polygonal section 110 of a nut 11.