PURPOSE: To prevent a plumb in an oil damper from being biased to come in contact with a vessel during long-term operation so as to prevent the action of minute vibration control from being lost by interposing an elastic body between the vessel and the plumb.

CONSTITUTION: If a high-speed movable body 6 stops or starts suddenly, by the viscosity of the oil 14 between the high-speed movable body 6, displaced relatively, and a plumb 15, the minute vibration of the high-speed movable body 6 attenuates, and functions as an oil damper. Since an elastic body 17 exists between this plumb 15 and the vessel 16, even if the plumb 15 tries to shift to one side during long-term operation, it only abuts on the elastic body 17, but it can not shift more. Accordingly, the plumb 15 can not make contact with the inwall of the vessel 16, being prevented by the elastic body 17.