Patent ID: 8623530

Claim:
A glass substrate for a magnetic disk, wherein the glass substrate is configured such that, in regions with respect to two places arbitrarily selected on a surface of the glass substrate on a central portion side relative to an outer peripheral end, a surface shape with a shape wavelength in a band of 60 to 500 μm is extracted from surface shapes in each of the regions and, assuming that a root mean square of the surface shape is given as a microwaviness (MW-Rq), a difference between the microwavinesses (MW-Rq) of the regions is 0.02 nm or less, and a ratio between the microwavinesses (MW-Rq) of the regions is 1.1 or less, wherein one of the two places is a region along a circumferential direction falling within a range of radius 31.5±0.05 mm from a center of the glass substrate while the other place of the two places is a region along the circumferential direction falling within a range of radius 25±3 mm from the center of the glass substrate, wherein the microwaviness (MW-Rq) is measured using a laser Doppler vibrometer, and wherein an average value of the microwaviness (MW-Rq) on a main surface of the glass substrate is 0.4 nm or less.