Patent ID: 8360824

Claim:
A method of processing a synthetic quartz glass substrate, comprising putting a polishing part of a rotary small-sized processing tool having a rotational axis set in a direction inclined relative to a normal to the substrate surface in contact with a surface of the synthetic quartz glass substrate in a contact area of 1 to 500 mm 2 , and scanningly moving the polishing part and substrate surface relatively while rotating the polishing part so as to polish the substrate surface, wherein the processing tool is put into reciprocating motion in a fixed direction on the substrate surface, and is advanced at a predetermined pitch in a direction perpendicular to the direction of the reciprocating motion on a plane parallel to the substrate surface, as the polishing proceeds, and wherein the reciprocating motion is performed in parallel to the direction of a projected line obtained by projecting the rotational axis of the processing tool onto the substrate.