Abstract: A method of smoothly processing a surface of crystal material, particularly a quartz crystal, to attain a good surface roughness and degree of eveness without substantial hillocks or micro-projections, without performing grinding or polishing processing. After lapping the surface of the crystal material, the lapped surface is etched with hydrofluoric acid. Finish etching is performed on the crystal material by buffer hydrofluoric acid as needed. In the manufacture of a crystal piece used in a crystal device, after the crystal wafer cut out from the rough crystal stone to the specified thickness is lapped, it is roughly etched to the desired thickness by hydrofluoric acid. Then, after ultrasonic washing by pure water, the crystal wafer is processed to the desired high quality of surface roughness, level of smoothness and thickness. The surface processing can be performed more easily, in less time, and with less labor than conventional methods, the cost is decreased, and productivity rises.