In a liquid-sealed type vibration isolator having a first orifice flow channel 56 and a second orifice flow channel 60, a valve member 66 formed of a rubber elastomeric membrane for opening and closing the second orifice flow channel 60 is provided on a partitioning member 40 so as to be orthogonal to the direction of flow in the second orifice flow channel. The valve member is held at the outer peripheral portion thereof by a wall surface of a valve housing chamber 68, and includes inside the outer peripheral portion thereof a membrane portion 66B which is subjected to the flexural deformation by the liquid flow in the second orifice flow channel to close openings 60C and 60D of the second orifice flow channel. Communicating holes 76 which bring the second orifice flow channel into communication are provided at positions not overlapped with the opening of the membrane portion 66B. Accordingly, the switching of characteristics is enabled with an inexpensive structure.