PURPOSE: To prevent a thin blade grinding wheel from face deflection and to eliminate the generation of scratch and crack of a cutting face, by interposing both faces of a thin blade grinding wheel which is rotated at a high speed by the air current whose flow quantity and pressure are controlled.

CONSTITUTION: Compressed air 9a and 9b fed to a nozzle 8 simultaneously with the rotation of a spindle shaft 1 generate an uniform pressure between both walls of the semi-disc like groove thereof and both planes of a grinding wheel 3, interposing the grinding wheel 3. The face deflection can thus be prevented.