PURPOSE: To improve the deceleration of a light article by communicating one chamber to be partitioned by a free piston with a cylinder chamber to form an inter-electrode orifice in the clearance between positive and negative electrodes, making the other chamber as a gas chamber, and using the electroviscous fluid where the viscosity is changed by applying the voltage to the positive and negative electrodes.

CONSTITUTION: An orifice 4 is provided corresponding to a hollow piston rod 3, and two chambers, i.e., a relief chamber R2 and a reservoir R3, are formed by a slidable free piston 8. The relief chamber R2 is communicated with a cylinder chamber and positive and negative electrodes 6 are provided inside thereof, and an inter-electrode orifice 7 is formed by the clearance between the electrodes 6. The reservoir chamber R3 is a gas chamber, and the voltage corresponding to the mass to be applied to a cylinder 1 and the hollow piston rod 3 is applied to the positive and negative electrodes 6 by a power supply equipment E to change the viscosity of the electroviscous fluid by the voltage. The deceleration of a light article can be remarkably improved thereby.