Chemical vapor deposition (CVD) diamond has outstanding properties, including low thermal expansion, high chemical resistance and high acoustic propagation and has been widely used in optical, electrical, mechanical, chemical and thermal applications. Since synthesized diamond film results in large surface roughness, the surface treatment or polishing should be applied to expand the applications. Although reducing surface roughness by mechanical and etching methods have been investigated, the cost on the complicated equipment and on the long processing time is the most particular important issue. A new method is developed in the present study to approach the smooth surface by a catalytic grinding wheel. As grinding, the catalytic reaction occurs at the contact area between the grinding wheel and the diamond surface, and sp3 structure of diamond can be converted to sp2 structure with lower bonding energy; therefore, the lower surface roughness. Consequently, the average surface roughness is extremely improved from 230 nm to 20 nm, and the processing time can be shortened 10 times more than conventional methods, either lapping, or chemical assisted lapping.