To suppress dispersion of chamfering, generation of a crack, or the like by cutting off the ridge part of a quartz oscillating plate of circular shape or rectangular shape by a laser beam.

A quartz oscillating plate 1 is pinchedly held with a chuck holder, a laser beam is continuously obliquely irradiated to the ridge part 10, and the laser beam is relatively moved to chamfer the plate. Recently, for example, a laser beam of wavelength suitable for cutting quartz is developed, it is partially put to practical use, and the cut-off face by a laser beam can be finished into a comparatively good condition. The many quartz oscillating plates and abrasive are charged into a barrel, and the barrel is rotated for a fixed time for polishing. For the abrasive used at this time, for example, abrasive of mesh of about No.600 is used. Because the polishing time is fundamentally for regulating the surface condition of a chamfering territory, the working time is enough to be short to the extent of polishing for about 5-6 hours.