A liquid-sealed antivibration device capable of improving the position accuracy of an outer fitting member and a diaphragm. An outer fitting member (11) is externally fitted on a partition member (20) with an interposition portion (10b) interposed, and the interposition portion (10b) is made to be fixed in thickness. Thus, when a diameter reduction process is given to a second attaching member (3), the outer fitting member (11) is restrained from being displaced in a direction to slip out of the partition member (20). Therefore, the outer fitting member (11) is restrained from falling eccentric or inclined relative to the partition member (20), and hence, it can be realized that the outer fitting member (11) and the diaphragm (10) are improved in position accuracy.