In an antivibration device (1), a partition plate (45) includes a main partition plate (46) made of an elastic material interposed between a protruding portion (60) and a support portion (54), and a reinforcement member (47) which is buried in the main partition plate (46) and is configured of a hard body that is harder than the main partition plate (46). The main partition plate (46) divides a main liquid chamber (9A) and a sub-liquid chamber (9B), and blocks the opening end of the hard member (50). A space surrounded by the hard member (50) and the main partition plate (46) constitutes a restriction passage (10). In the main partition plate (46), a communication portion (42) that penetrates therethrough in an axial direction and causes the main liquid chamber (9A) and the restriction passage (10) to communicate is formed. The reinforcement member (47) is disposed to surround the peripheral edge of the communication portion (42) in the main partition plate (46).