Abstract: A process and an apparatus for positioning a substrate provided with at least an alignment mark (reference pattern) and other patterns irrelevant to the alignment such as circuit patterns, are featured by obtaining photoelectric signals corresponding to the pattern distribution in a scanning area extending over a determined length in a scan direction crossing said reference pattern at a determined angle and containing the reference pattern, identifying that a photoelectric signal satisfying at least a condition in the scan direction is generated by the reference pattern and aligning the substrate according to thus identified photoelectric signal.