A method of manufacturing a mask blank substrate, comprising:
- a preparation step of preparing a transparent substrate having a precision-polished main surface;
- a shape measurement step of measuring height information of the main surface from a reference plane at a plurality of measurement points set in an actual measurement region of the main surface, thereby obtaining a before-chucking main surface shape;
- a simulation step of obtaining, through simulation, an after-chucking main surface shape which is height information of the main surface from the reference plane at the plurality of measurement points when the transparent substrate is chucked on a mask stage of an exposure apparatus;
- an approximate curved surface calculation step of calculating an approximate curved surface based on the after-chucking main surface shape;
- and
- a recording step of recording information of the approximate curved surface in a recording apparatus in association with the transparent substrate.