The present invention provides a fabrication method for a magnetic disk-use glass substrate on which ultraclean cleaning can be carried out without degrading, insofar as possible, the smooth surface obtained from precision polishing. In this magnetic disk-use glass substrate fabrication method, after the step in which the magnetic disk-use glass substrate has been given a mirror surface polish, the glass substrate is cleaned by being exposed to a cleaning solution that can etch the glass substrate and that contains at least guanidine or imidazole. In addition, the cleaning is performed while keeping the total quantity of sodium ions and potassium ions in the cleaning solution to under 200 ppm.