PURPOSE: To provide an active vibration isolation device with improved vibration isolation performance by improving the characteristics of an electric-pneumatic pressure analog valve, and control the pneumatic pressure to be fed to the electric-pneumatic pressure analog valve to a constant value, and thereby improving the controlling accuracy of the pneumatic pressure of an air spring.

CONSTITUTION: A vibration control loop is formed by a vibration sensor, a displacement sensor 15, and an actuator which is driven by the acceleration signal, the velocity signal and the displacement signal to be obtained from the vibration signal and inputs the control force to a subject 13 to be controlled, and at the same time, a displacement control loop is formed by an electric- pneumatic pressure analog valve 22 which is driven by the displacement signal and the displacement quantity signal to be obtained from the displacement signal, and adjusts the pneumatic pressure of an air spring 12. Thus, the control of the vibration of the subject 13 to be controlled is executed by the vibration control loop of the air spring 12 through the vibration sensor and the displacement sensor 15, while the control of the displacement is executed by the displacement control loop of the air spring 12 through the displacement sensor 15, enabling the displacement control of the micron unit in the vertical direction.