Patent ID: 7985494

Claim:
A glass substrate for a magnetic disk that is mounted on a hard disk drive, wherein the glass substrate satisfies 0.4 nanometer <Ra 1 ≦0.8 nanometer, 0 nanometer <Ra 1 −Ra 2 ≦0.2 nanometer, 0.5 nanometer ≦Wa 1 ≦0.6 nanometer, Wa 2 ≦0.65 nanometer, and 0.05 nanometer ≦Wa 2 −Wa 1 ≦0.15 nanometer where Ra 1 is an average surface roughness of a first annular area between 1 millimeter and 3 millimeters outward from an inner periphery of a main surface of the glass substrate, Ra 2 is an average surface roughness of a second annular area between 1 millimeter and 3 millimeters inward from an outer periphery of the main surface, Wa 1 is an average waviness height of the first area in a circumferential direction of the glass substrate having a cycle of 300 micrometers to 5 millimeters, and Wa 2 is an average waviness height of the second area in the circumferential direction having a cycle of 300 micrometers to 5 millimeters, the surface roughness of the glass substrate continuously increases from the outer periphery to the inner periphery of the glass substrate, and the average waviness height of the glass substrate continuously decreases from the outer periphery to the inner periphery of the glass substrate.