PURPOSE: To prevent the excess increase of the mass of a device by detecting displacement between the machine body of the mounting part of an isolator through which a cabin is supported in a suspension state to a machine body, determining a relative speed through differentiation of the relative displacement, and controlling operation of the isolator by means of the relative displacement and the relative speed.

CONSTITUTION: A cabin 10 is independently supported in a suspension state to a helicopter body 11 through four vertical isolators 1, isolators 1 located one at each end in a lateral direction, and four isolators 1a in the vertical direction of the lower part of the cabin 10. Relative displacement between the machine body 11 of the mounting parts of the isolators 1 and 1a and the cabin 10 is detected by a displacement sensor 4, and the detected relative displacement is differentiated by a differentiator 5 to calculate a relative speed. The generation of vibration is suppressed by a controller 6 by regulating a damping force through control of opening and closing of the valves of the isolators 1 and 1a based on the relative displacement and the relative speed.