Abstract: There are included a base rail in an elongated shape fixed to the roof face, a holder supporting member movable in a longitudinal direction of the base rail by being guided by the base rail and a holder fixing member provided at the holder supporting member. Thereby, it is not necessary to accurately fix the base rail to the roof face. Further, the holder supporting member supports a holder for holding an object to be installed and presses a predetermined portion of the holder to the base rail by the holder fixing member. Thereby, fixing of the base rail and the holder supporting member and fixing of the holder supporting member and the holder can be achieved in one motion by one pressing member and the number of steps with regard to attaching the holder can be reduced.