A polishing composition contains silicon dioxide, an alkaline compound, and water. Silicon dioxide is, for example, colloidal silica, fumed silica, or precipitated silica. The alkaline compound is, for example, ammonium carbonate, potassium carbonate, sodium carbonate, ammonium hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, ammonium phosphate, potassium phosphate, sodium phosphate, ammonium hydrogen phosphate, potassium hydrogen phosphate, or sodium hydrogen phosphate. The polishing composition can be suitably used in applications for polishing a glass substrate.