A manufacturing method of a glass substrate for a magnetic disk is provided whereby nano pits and/or nano scratches cannot be easily produced in polishing a principal face of a glass substrate using a slurry containing zirconium oxide as an abrasive. The manufacturing method of a glass substrate for a magnetic disk includes, for instance, a polishing step of polishing a principal face of a glass substrate using a slurry containing, as an abrasive, zirconium oxide abrasive grains having monoclinic crystalline structures (M) and tetragonal crystalline structures (T).