To perform tuning the notch frequency of a dynamic spring constant further to the low frequency side as interference of an umbrella-form member is prevented from occurring.

A pair of first and second mounting members 1 and 2 separated away from each other in a vibration input direction are intercoupled through an elastic support body 3. A liquid chamber 4 filled with liquid 6 is partitioned between the elastic support body 3 and a diaphragm 5. The liquid chamber 4 is partitioned into a pressure receiving chamber 8 and a balance chamber 9 by a partition body 7 having an orifice 14. An umbrella-form member 10 is disposed in a pressure receiving chamber and the interior of the pressure receiving chamber is partitioned into a main chamber 8a and an auxiliary chamber part 8b which are intercommunicated through a gap 15. The top part of the auxiliary part is sealed with air 16, and the expansion spring of the elastic support body is reduced in an apparent manner through a volume spring of seal air due to the increase of the inner pressure in the auxiliary chamber during input of high frequency vibration. In a seal amount of air, the volume spring is set to a value in a range of 1/2-1/4 of the expansion spring and 0.5-10cc, preferably 1.5-3cc. Filling with air is effected in such a state that with upside down, the elastic support body is deformed through downward displacement of the first mounting member and in such a state that a seal space is formed between the umbrella member and the first mounting member or filling with the liquid 6 is effected in such a state that the umbrella member having a recessed part is brought upside down.