Vibration isolation device

A vibration isolation device comprising:

• a cylindrical first mounting member connected to one of a vibration generating unit and a vibration receiving unit and a second mounting member connected to the other thereof;
• an elastic body connecting the first mounting member and the second mounting member;
• and
• a partition member which partitions a liquid chamber in the first mounting member into a main liquid chamber including the elastic body as a part of a partition wall thereof and a sub liquid chamber, wherein
• the partition member includes:
• a membrane which forms a part of the partition wall of the main liquid chamber;
• and
• a first orifice passage which communicates with the main liquid chamber and opens toward the sub liquid chamber,
• a flow resistance of a liquid in a portion positioned on the main liquid chamber side and a flow resistance of a liquid in a portion positioned on the sub liquid chamber side are different from each other in the first orifice passage,
• the first orifice passage is constituted by a first orifice groove positioned on the main liquid chamber side and extending in a circumferential direction, a second orifice groove positioned on the sub liquid chamber side and extending in the circumferential direction, and a connection hole, and
• the connection hole connects in a radial direction an end portion on one side in the circumferential direction of the first orifice groove and an end portion on one side in the circumferential direction of the second orifice groove, the end portion on the one side in the circumferential direction of the first orifice groove and the end portion on the one side in the circumferential direction of the second groove being disposed at equivalent circumferential positions.