PURPOSE: To reduce the dynamic spring constant in wide frequency ranges by forming a bevel-shaped member so that the rigidity of the member itself can be changed.

CONSTITUTION: One end in vertical direction of a supporting cylinder 8 is coupled with the car body side while a mounting member 3 is coupled with the other end through a resilient bearing piece 4, and this is coupled with the engine side. The inside liquid chamber 9 is partitioned by a partitioning member 6 into a pressure receiving chamber 9a and an equilibrium chamber 9b, and the two are put in communication through an orifice 12. A bevel-shaped member 7 is installed on the mounting member in such a way as protruding to the pressure receiving chamber side. This bevel-shaped member is formed from an upper and a lower resilient diaphragm member where an electroviscous liquid E is encapsulated in the inside, and the diaphragm members are made from an electroconductive rubber so that electrodes 18, 19 are accomplished. The impressed voltage is controlled by a control means 26 so that the rigidity of the bevel-shaped member is changed, and thereby the frequency range where a ruduction of the dynamic spring constant occurs s varied.