A glass substrate for an information recording medium is manufactured by polishing the surface of a raw material glass plate. The polishing of the raw material glass plate is divided into a step for performing a first polishing process to roughly polish the surface of the raw material glass plate to be smooth and a step for performing a second polishing process to finely polish the surface of the roughly polished raw material glass plate to be smoother. The first polishing process uses a polishing pad made of a synthetic resin foam and slides the polishing pad on the raw material glass plate surface while supplying a polishing agent to roughly polish the surface. A pad dressing process is performed on the polishing pad before being used in the first polishing process. The pad dressing process polishes the surface of the polishing pad by sliding the polishing pad on a pad dresser including abrasive grains.