To improve damping characteristics with small energy by arranging an actuator for applying force to a support element in a direction along reaction, and a control system for causing motion of the actuator suitable for minimizing displacement of a mass element of a main system.

A support element S has a mass Mo, and receives reaction from a spring element 22, and a damping element 23 in respect to a mass element 21. An active damping device A is serially arranged to a passive damping device p through the support element S. The active damping device has an actuator 24 arranged between the support element S and the mass element 11 for applying force to the support element S in the direction along the repulsion, and a control system 25 for causing the motion of the actuator 34 suitably for minimizing displacement of the mass element 11. Damping characteristics of the passive damping device are not affected by mechanical resistance of the actuator and the damping element. It is thus possible to improve damping performance in respect to an object with small size and energy.