An object of the present invention is to provide a polishing method for diminishing concave defects of a glass substrate used in a reflective mask for EUVL and the like. The invention relates to a method of polishing a glass substrate which comprises polishing a major surface of the glass substrate while feeding a polishing slurry between the glass substrate and a pad surface of a polishing pad, wherein the polishing load of the polishing pad is from 1 to 60 g/cm.sup.2. The pad surface of the polishing pact is preferably dressing-processed.