To provide a fluid sealed cylindrical vibration isolating device to exert a vibration isolating effect on the basis of the fluid flowing action through an orifice passage between a plurality of main liquid chambers in which a non-compressive fluid is sealed, in which the vibration isolating characteristics, in particular the spring constant, can be varied to a great extent in accordance with the input vibration, etc.

A first and a second main liquid chambers 70, 72 are provided opposingly in the main vibration input direction, and a third and a fourth main liquid chamber 74, 76 are formed in a bulkhead part in the circumferential direction of the first and second chambers 70, 72, and the configuration further includes an orifice passage 104 connected with the second chamber 72 and admitting flowing in and out of the fluid to/from the chamber 72 and a communication passage (112) to put the third 74 and fourth chambers 76 in mutual communication. The orifice passage 104 and communication passage (112) are changed over simultaneously between communication and shutoff by a valve means 120.