As a measure against vibration caused by disturbance due to mass eccentricity of a disc, a conventional disc device has a means to add an auxiliary mass that passively operates. This method has no way to enhance vibration damping effect other than setting the auxiliary mass to be large, and therefore there is a problem that the device becomes large. An auxiliary mass 300 is actively driven by an auxiliary mass driving portion 360. The driving of the auxiliary mass 300 is performed by amplifying a signal corresponding to a force transmitted from a main frame portion 100 to the auxiliary mass 300. This achieves a vibration damping effect using the small auxiliary mass 300 to the same degree as that where the large auxiliary mass is mounted.