To provide a magnetic-disk glass substrate manufacturing method that can reduce the inner diameter dimensional error.A magnetic-disk glass substrate manufacturing method of this invention including a chemical strengthening step of bringing a plurality of glass substrates 102 into contact with chemical strengthening treatment solutions of a plurality of chemical strengthening treatment baths 130, respectively, to chemically strengthen the glass substrates further includes an inner diameter measuring step of measuring the inner diameter of each of the glass substrates 102 before the chemical strengthening step, a grasping step of grasping a variation of the inner diameter of the glass substrate 102 to be generated by the chemical strengthening step for each of the chemical strengthening treatment baths 130, and a combination determining step of determining the chemical strengthening treatment baths 130, that perform chemical strengthening, based on the variations so that the inner diameters of the glass substrates, whose inner diameters are measured, after the chemical strengthening step become a desired value. In the chemical strengthening step, the glass substrates 102 are chemically strengthened in the determined chemical strengthening treatment baths 130, respectively.