PURPOSE: To absorb or damp oscillation of a multi-floor building by arranging a horizontally slidable mass on an arcuated rail laid on a higher floor of the building so that the mass is accelerated by a linear motor.

CONSTITUTION: A mass 4 incorporating wheels 3, 3 are set on an arcuated rail 2 having an radius (r) laid on the topmost floor or a floor 1 near thereto of a multi-floor building so that the mass 4 can slide on the rail 2. Then, the mass 4 is subjected to pendulum motion on the rail 2, and the radius (r) of the rail 2 is set so that the cycle period of the pendulum motion is coincident with the natural period of the building in order to obtain a passive vibration absorber. Further, an armature 5 of a linear motor is attached to the mass 4, and stators 6 of the same are arranged arcuately along the rail 2. Further, the motions of the building and the mass 4 are measured, and the speed of the linear motor is controlled in accordance with the measured data by a computer, thereby it is possible to provide a passive type vibration absorber.