Patent ID: 8399163

Claim:
A method of detecting an alignment mark for aligning a photomask with an exposure region of a base material when said base material is subjected to exposure processing, wherein said base material has said alignment mark, and has a mark for searching in a different position from a position of said alignment mark, and said method comprises the steps of: previously storing a positional relationship between said alignment mark and said mark for searching; acquiring an image of said base material as a first image by photographing said base material by an imaging device; calculating a distance by which said base material is to be moved for causing said alignment mark to exist within an imaging area of said imaging device based on the position of said mark for searching in said first image and said stored positional relationship when said alignment mark does not exist and said mark for searching exists in said acquired first image; moving said base material by said calculated distance; acquiring an image of said base material as a second image by said imaging device after said base material is moved; and detecting the position of said alignment mark that exists in the acquired second image.