A booster is used to modify the amplitude of vibration applied to the cutting tool through the horn and to provide a clamping point for more rigid stack mounting. The horn is of stepped type with a gain of 1:1. The diamond tool tip is installed to the end of the vibrated horn in such a way that the rake face is oriented downward. Since it is expected that an acceleration of tens of thousands of gravity is applied to the tool tip, this diamond cutting tool is especially designed with the consideration of minimizing the effect of tool weight. The tool tip is vibrated in the axial direction of the horn at a resonant frequency of 40 kHz.