switching regulating operation introducing a negative pressure and an atmospheric pressure into the change over chamber 12 which is provided along with the main liquid chamber 7 first and second auxiliary liquid chambers 8 9 first and second orifices 13 14 and first and second diaphragms 4 11 and which is adjacent to the second auxiliary liquid chamber 9 joined to the second orifice 11 of a lower liquid passage resistance in the vibration isolator thus assembled the partition plate member 16 which presses the second diaphragm 11 to form the second auxiliary liquid chamber 9 and second orifice 14 is fitted firmly in an engaged state around the outer circumference of the main partition member 15 by a swaging device for the same outer circumference therefore the main partition member 15 and partition plate member 16 are combined together thus preventing their being separated from each other and the second diaphragm 11 is retained in a pressed state reliably accordingly even when the fluctuation of the liquid pressure ascribed to the vibration of the vibration isolating base member 2 and permanent set in fatigue of parts due to heat occur there is not the possibility that the deficiency of the sealability of parts and the short circuiting of orifices occur when the partition plate member 16 is swaged to the main partition member 15 as mentioned above the circumferential edge portion of the second diaphragm 11.