A window regulator includes a wire sag compensating mechanism. The wire sag compensating mechanism includes an outer tube arranged between the vicinity of a drum and at least one wire guide member allowing passage of a wire therethrough and fixed at an end on the side of the wire guide member to a member where the wire guide member may be provided. A tube holding portion may be provided on a member on which the drum is provided allowing movable engagement of the drum side of the outer tube and guiding the drum side of the outer tube in the axial direction of the outer tube. A spring may be provided for urging the drum side of the outer tube away from the drum. A disengagement restricting arrangement (e.g., projections and elongated holes) may be provided for restricting the outer tube from disengaging from the tube holding portion.