A process for producing a polishing composition excelling in dispersion stability wherein the amount of agglomerated particles is reduced. In step 1-1 thereof, ultrapure water is adjusted so as to have a pH value of 1.0 to 2.7. Under shearing force given by a high shear disperser, fumed silica powder of 50 to 200 m.sup.2/g specific surface area is charged therein until an initial silica concentration of 46 to 54 wt %, and the high shear disperser is operated so as to apply shearing force for 1 to 5 hours. In step 1-2, a small amount of ultrapure water is added to the silica dispersion so as to realize a silica concentration of 45 to 53 wt % and shearing force is applied for 10 to 40 minutes. In step 1-3, ultrapure water is added to the silica dispersion so as to realize a silica concentration of 33 to 44 wt % and shearing force is applied for 0.5 to 4 hours. In step 2-1, the silica dispersion is added to an aqueous basic substance solution prepared so that a pH value after mixing is in a range of 8 to 12 and so that silica concentration is in a range of 10 to 30 wt %.