A method for manufacturing a magnetic disk comprises the step of applying a continuous laser beam to both sides of a glass workpiece and etching both sides of the workpiece with an aqueous acidic fluoride-containing etching solution. The portion of the workpiece receiving the laser beam etches at a much faster rate than the portions of the workpiece that were not exposed to the laser beam. The workpiece is then broken along a line or curve formed by the above-mentioned steps. The resulting structure is a substrate used to form a magnetic disk. The disk is completed by depositing an underlayer, a magnetic layer and a protective overcoat on the substrate.