Abstract: A magnetic disk substrate manufacturing method of this invention includes a main surface polishing process that polishes disk-shaped glass substrates by the use of a polishing machine having a carrier pressed between a pair of polishing surface plates and adapted to make an orbital motion while rotating on its axis in a state of holding the disk-shaped glass substrates. In the polishing machine, the carrier is placed in a state where a plate-like member is disposed on one side of main surfaces of the disk-shaped glass substrate, so that only the other side of the main surfaces of the disk-shaped glass substrate is polished while allowing the one side of the main surfaces of the disk-shaped glass substrates to be a non-polishing main surface.

Abstract: A glass substrate is for use in a magnetic disk. The glass substrate is formed by using a plate-like glass produced by a float method and having a pair of main surfaces. One surface of the main surfaces, which is formed with a tin layer when producing the plate-like glass by the float method, is caused to serve as a surface not for use in magnetic recording and the other surface formed with no tin layer is caused to serve as a surface for use in magnetic recording.

Abstract: In a magnetic disk substrate having first and second chamfered faces respectively connecting between first and second main surfaces opposite to each other and an edge face located between the first and second main surfaces, the ranges of the first and second chamfered faces are specified. Specifically, the distance a from a first boundary portion being a boundary between the first main surface and the first chamfered face to a point of intersection between the first main surface and an extended line of the edge face and the distance b from a second boundary portion being a boundary between the second main surface and the second chamfered face to a point of intersection between the second main surface and an extended line of the edge face are set to satisfy a/b?1.6.