To apply beautiful carving not almost leaving a caving mark to a nonmetal material such as glass, ceramics, a jewel or the like.

In such a state that a grinding material is present on the surface of a member 16 being the nonmetal material, a tool 14 vibrated in a Z-direction on the basis of the signal received from an ultrasonic oscillator is appropriately moved not only in the Z-direction but also in an XY direction to apply carving to the member 16.