The object of the present invention is to enable efficient vibration processing by applying a sufficient displacement amount and response speed to an object to be vibrated. In grinding of an outer surface of a workpiece W, first and second supporting members are provided for supporting two opposed points of the workpiece, and first and second vibrators comprising a plurality of piezoelectric elements are arranged in blind holes formed in the center of the first and second supporting members. The first and second vibrators are activated with sine wave signals which differ in phase by 180 degrees so as to cause the first and second supporting members to expand and shrink in the back-and-forth direction. The displacement amount is amplified and the processing is performed. Also, the second supporting member can move back and forth toward the first supporting member.