There is provided a polishing method for polishing a non-oxide single-crystal substrate such as a silicon carbide single-crystal substrate at a high polishing rate to obtain a high-quality surface that is smooth and excellent in surface properties. This polishing method is a method of supplying a polishing liquid to a polishing pad not including abrasive grains to bring a surface to be polished of the non-oxide single-crystal substrate and the polishing pad into contact with each other and polishing the surface to be polished by a relative movement between them, the method characterized in that the polishing liquid comprises: an oxidant whose redox potential is 0.5 V or more and which contains a transition metal; and water, and does not contain abrasive grains.