The present invention is to provide a method for processing the whole of a glass substrate surface so as to give a surface excellent in flatness and surface roughness. The present invention provides a method of processing a glass substrate surface using a processing technique selected from the group consisting of ion-beam etching, gas cluster ion-beam etching, plasma etching, and nano-ablation, wherein a frame element satisfying the following (1) and (2) is arranged along the periphery of the glass substrate before the glass substrate surface is processed: (1) the difference between the height of the frame element and the height of the glass substrate surface is 1 mm or smaller; and (2) the frame element has a width which is not smaller than one-half the beam diameter or laser light diameter to be used in the processing technique.