PURPOSE: To prevent generation of the surface damages such as scratches by executing the polishing operation so as to finish the surface smooth by supplying the polishing liquid whose working speed is small after the work-affected layer is removed by supplying the polishing liquid whose working speed is large at the specifed working pressure.

CONSTITUTION: When the substrate of the crystalline material such as a semiconductor is polished, the working precision is affected by the polishing conditions such as the working pressure for pressing the substrate against the polishing pad and the amount of the polishing liquid to be supplied to the polishing pad, and therefore as the first stage of the working, the working pressure is set to the pressure (e.g. 50g/cm2) surface flatness of the substrate may not deteriorated and the work affected layer is removed by using the amount (e.g. 10l/h) of the polishing liquid to be supplied whose working speed is large. Subsequently, as the second stage, the working pressure is set to the pressure (e.g. 100g/cm2) where the specified surface flatness is obtained and the polishing is executed so as to finish the surface smooth by using the amount (e.g. 5l/h) of the polishing liquid to be supplied whose working speed is small.