PURPOSE: To accelerate machining and easily control the machining quantity by specifying the ratio between the diameter of a fine grain and the width of a fine pattern in machining the surface of a ceramic substrate.

CONSTITUTION: Fine patterns each 3 having the width of 2-200μm are formed on a mask 2 having the thickness of about 2-100μm to cover a substrate 1. Fine grains 5 of alumina having the diameter of about 0.6-50μm are ejected from a nozzle 4 to collide with the mask 2, and fine machining is applied to the substrate 1 via the fine patterns 3. The diameter of the fine grain 5 is set to 0.1-0.3 times the width of the fine pattern 3. The substrate 1 and the mask 2 are moved in the X-X direction, and the nozzle 4 is moved in the Y-Y direction for machining. The machining quantity (difference between the surface heights before and after the machining of the substrate 1) is made smaller as the diameter of the fine grain 5 is made smaller.