1. An exposure apparatus for exposing an object to light, said apparatus comprising: a camera which captures an image of a mark on the object to obtain image data corresponding to the image; an extraction section which extracts an edge position in the image data obtained by differentiating the image data; a determination section which determines a position of the mark by comparing the extracted edge position with a template; and a control section which changes at least one of a parameter used by said extraction section and a parameter used by said determination section, based on a result of the comparing by said determination section, wherein the object to be exposed is positioned based upon the position of the mark determined by said determination section.