PURPOSE: To carry out chamfering with high efficiency by mounting a workpiece on a disk-like grinding wheel and surrounding the workpiece with a tubular wall plate to rotate the grinding wheel.

CONSTITUTION: A polishing section 1 is constituted from a disk-like grinding wheel 6, a support plate 7 mounting fixedly said grinding wheel and a rotary shaft 8 for rotating the support plate 7. A workpiece holder section 2 is constituted from a disk-like lid body 11 suspended vertically movably, a cylindrical wall plate 12 connected to the outer peripheral portion of lower end face of the lid body 11 and a retainer plate 15 mounted through a support lever 14 on the lid body 12 in a receiving space formed by the lid body 11 and the wall plate 12. A workpiece W is put in the receiving space 13 to be chamfered by a grinding wheel 6.