Abstract: An ultrasonic machining method for mirror-finishing with an extremely high precision the surface of a workpiece by supplying an electrolyte and soft spheres, in combination or separately, to the electrolysis region between the tool of an ultrasonic machine and the workpiece which are positioned a certain distance apart. Being ultrasonically actuated, the soft spheres bring about the fluid lubrication which removes the passive state film which forms on the work surface of the workpiece as electrolysis proceeds. In addition, the soft spheres catches and bring away the residues of the passive state film removed, owing to its ionic attraction. Thus ultrasonic machining is achieved without any mechanical force (machining stress) applied to the work surface.