A vibration isolator includes: a housing which is filled with a fluid; an intermediate plate inserted in the housing for partitioning the interior of the housing into two liquid chambers, the intermediate plate having therein a cylinder and at least two passageways for allowing the two liquid chambers to communicate with each other, the cylinder being formed at a position midway in one of the passageways, and one of the liquid chambers being provided with an elastic wall to render the capacity of that liquid chamber variable; a piston capable of opening and closing one of the passageways as the piston moves in the cylinder; and a pressure changeover valve disposed outside the housing and capable of moving the piston by means of a change in pressure by applying a gas pressure to the piston.