A vibration isolator designed to improve mounting facility is disposed between a vibration source and a base on which the vibration source is supported. The vibration isolator has an elastic member provided between the vibration source and the base to elastically support the vibration source, a main chamber in which a fluid is enclosed and the volume of which is changed according to a deformation of the elastic member, a sub chamber defined by an elastic membrane and communicating with the main chamber through an orifice, a moving member provided in a fluid chamber formed by the main and sub chambers, and an actuator for driving the moving member. The actuator is fixed to the elastic membrane in a fluid sealing manner, and drives the moving member from the outside of the fluid chamber formed by the main and sub chambers through attachment members connected to the moving member.