PURPOSE: To prevent the reduction in durability by using a piezoelectric device for a vibration source of an oscillator for reducing the vibration of vehicle, by carrying out heat exchange with an engine cooling water cooled through a radiator, and by maintaining the temperature of the piezoelectric device at a proper level.

CONSTITUTION: A case 9 of an oscillator 4 can be slid along the outer peripheral surface of a supporting piston 7, and a piezoelectric device 13 is arranged in the case 9. By changing the voltage applied to the piezoelectric device, the piston 7 is relatively oscillated, so as to offset the vibration of a vehicle. The maximum temperature of the cooling water in a lower tank 16 cooled by a radiator 1 is approximately 150°C, while the oil in an oil tank 17 is cooled by the cooling water, and is flown in an oil passage 14, so as to cool the piezoelectric device, and the oil is returned to the oil tank. In the initial stage of the cooling operation of an engine, since the elevation in temperature of the cooling water is rapid, the temperature reaches fast a proper level. The piezoelectric device is thus maintained at an appropriate temperature, and the reduction in the durability is thus prevented.