In previous papers, active vibration isolation systems are presented for deterministic disturbances. In this paper, it is shown that the system is also effective for random disturbances. For sine form disturbances optimum damping depends on the amplitude of disturbance vibrations. For random disturbances it is found that the same amount of damping becomes optimum by using an amplitude of the equivalent sine form vibrations which have same energy with that of the random vibrations. Optimum control gains are obtained through the same procedures as those of the previous papers. Delicate adjustments of those gains are made with the aid of micro computers.