A solenoid driving device with excellent electric power efficiency which drives and controls an actuator including a solenoid and an active vibration isolating support device which includes the solenoid driving device are disclosed. The solenoid driving device includes a booster circuit which boosts a battery voltage, and driving circuits which an actuator with the electric power supplied and boosted by the booster circuit. ACM_ECU200A including a micro computer calculates the magnitude of the vibration of the engine, an engine vibration cycle and a phase lag to obtain the drive frequency of the actuator in the vibration state estimating unit and the phase detecting unit. A booster circuit controlling unit of the micro computer determines the target voltage based on the drive frequency. The target voltage is input to the booster circuit, and the booster circuit supplies the required electric power to the driving circuits at the target voltage.