PURPOSE: To polish the surface of ceramic highly efficiently and accurately by employing a polishing surface plate where soft glass is employed as binder while hard glass is dispersed and secured such that a portion will project from the surface.

CONSTITUTION: The surface plate 14 is formed while employing soft glass having low melting point such as soda glass as the body 11 then mixing with hard silicon glass powder 12 and employing the soft glass as binder such that a portion will project about 1.2μm. When mounting a work (silicon nitride) 13 on the surface plate 14 and polishing while moving relatively, the working liquid 15 containing cerium oxide abrasive grains placed in proper gap between the projected abrasive grain 12 and the surface plate 14 will function efficiently with strong pressure between the surface 16 of projected abrasive grain 12 and the work 13 thus to perform polishing. It will never cause increase of polishing resistance due to adsorption between the surface plate body 11 and the work 13. Consequently, a plane can be polished efficiency and highly accurately without causing warp or distorsion.