A structure for shielding a rail includes a rail configured to be mounted on a vehicle body, a drive unit movably connected to the rail, a swing arm rotatably connected to the drive unit and a sliding door, a shade bar configured to be in contact with the swing arm and connected to the drive unit so as to be movable in a first direction in which the shade bar moves close to the rail or a second direction in which the shade bar moves away from the rail, and a cover having a first end connected to the shade bar, the cover configured to open or close a space in which the rail is positioned in accordance with a movement of the drive unit.