In a flange-nut posture control device includes a first opening, a direction controlling portion is constituted by two vertical wall portions extending in a vertical direction such that the vertical wall portions are distanced from each other to face each other via a space with a distance smaller than the diameter of a flange portion of the flange nut. A lower guide portion is provided such that a V-shaped groove having a bottom portion between the vertical wall portions extends to be inclined from a horizontal plane. A second opening is surrounded by at least the vertical wall portions and the lower guide portion and formed such that the flange nut is passed through the second opening. An outlet groove portion is connected to the lower guide portion at an end surface of the second opening and extends with the same inclination as the lower guide portion.