The winding drum of the cable-winding device is kept air-tight by an air-tight container. A lower elastic sealing member 1a is interposed between the air-tight container and the rotation table. The air-tight container, the lower elastic sealing member 1a, and the chamber are communicated with one another. The air-tight container and the chamber are filled with inert gases at less than atmospheric pressure. The rotation table, the weight sensors, the drive motor, the gear are disposed in the atmosphere. An arm is vertically installed on the rotation table. An upper elastic sealing member 1b is interposed between the end portion of the arm and the air-tight container. The upper elastic sealing member is communicated the interior of the air-tight container through a through hole. The arm support the top portion of the upper elastic sealing member.