PURPOSE: To keep the vibrating level of a structure at a low level even if the exciting frequency of vibration inputted into the structure changes, and achieve change control for frequency which provides the lowest vibration level.

CONSTITUTION: A piezoelectric element (b) is mounted on a structure (a), and voltage is applied to the piezoelectric element (b) so that low vibrating level may be achieved for the exciting frequency of vibration to be inputted into the structure (a), and internal tensile force and internal compressive force is given to the structure (a) by the piezoelectric element (b) to form a means for chancing the characteristic frequency of the structure (a). Moreover, a characteristic frequency control means (d) is formed into a means for controlling applied voltage to the piezoelectric element, (b) according to vibrating level characteristics data which are measured as parameters beforehand.