In a vibration preventing damper forming method and a vibration preventing damper integrally formed with a mechanical chassis according to the present invention, an opening side end portion 9e of a damper housing 9 and a vibration preventing damper forming portion of a mechanical chassis 6 are made of a resin. The damper housing 9 is mounted on the vibration preventing damper forming portion by the fixture of the resin portions. Thus, a vibration preventing damper 8 is integrally formed with the mechanical chassis 6. For this reason, in supporting in a vibration proof manner and in a floating matter the mechanical chassis 6 within an interior of a casing 10 by means of the vibration preventing damper 8, it is possible to improve the working efficiency in mounting the mechanical chassis 6 to the casing 10 and to cope with the requirement of miniaturization of a mounting space between the interior of the casing 10 and the mechanical chassis 6.