To prevent an oxide film from being formed on a face to be ground of a workpiece by carrying out a grinding process in vacuum or nitrogen gas for grinding.

An ordinary wet grinding method in which an abrasive liquid is supplied between a face to be ground of a workpiece and a buff wheel to grind the face to be ground of the workpiece is used. In this case, a single buff or a plurality of buffs may be used. Moreover, the abrasive liquid which is used usually may be used. To bring the face to be ground of the workpiece into vacuum atmosphere, for example, the whole grinding device is covered with a casing, and its inside is sucked by a suction pump to bring it into a vacuum condition. Alternatively, only the face to be ground of the workpiece may be covered with a casing. Moreover, to bring the face to be ground of the workpiece into nitrogen gas atmosphere, nitrogen gas is filled in the casing.