A method of setting control data by an active vibration isolation control system includes the steps of selecting, when a frequency of a pulse signal actually detected is superior to a predetermined frequency, appropriate control data selected from among predetermined data maps incorporating control data capable of securing, in accordance with various vehicle driving conditions respectively, a control condition in which operation of the vibrator is preferably controlled, calculating a deviation between the appropriate control data commensurate with the actual vehicle driving condition at the time of controlling and actually detected data representing vibration subjected to a vehicle specific position, the actually detected data obtained in terms of a same physics amount as a physics amount of the control data, and modifying the appropriate control data on the basis of the calculated deviation.