To reduce occurrence of flaws in a polishing process by preventing an abrasive grain or metallic particles deposited on the surface of a glass substrate for a magnetic disk in a lapping process from entering into the subsequent polishing process. A lapping process for the main surface is a glass substrate for a magnetic disk is conducted; an etching process for the main surface of the glass substrate is conducted to the extent of a depth of 0.1 .mu.m to 3 .mu.m, followed by conducting a polishing process for the main surface of the glass substrate where the etching process has been conducted.