A process for polishing a glass substrate, which enables to polish a glass substrate having a large waviness formed by mechanical polishing, to have a surface excellent in flatness, is provided. A process for polishing a glass substrate, comprising a step of measuring the surface profile of a mechanically polished glass substrate to identify the width of waviness present in the glass substrate, and a step of applying dry etching using a beam having a beam size in FWHM (full width of half maximum) value of at most the above size of waviness, to polish the surface of the glass substrate.