PURPOSE: To uniformalize the distribution of load added on a processed matter and restrain tapering occurring at the processed matter after processing, by conducting abrasion by making the center of pressurization eccentric against the circular arc center of the processed matter according to the shape of the processed matter.

CONSTITUTION: A sheet like processed matter 4 having an approximately uniform thickness is processed in abrasion while it is being retained in pressurization by means of a pressurization plate 3 on a lower fixed tray 1. In this instance, processing in abrasion is done by making eccentric the center p of pressurization against the center o of the circular arc of the processed matter 4 according to the plane shape of the processed matter 4. As a result, the distribution of the surface internal pressure of the processed matter 4 can be uniformalized, and the occurrence of tapering occurring at the processed matter 4 can be drastically restrained.