A position detection apparatus for and method of detection the position of a pattern formed on a substrate (e.g, a wafer). The apparatus (100) comprises an illumination system capable of illuminating the pattern, and an imaging optical system arranged to converge light from the substrate (126) to form an image of the pattern. The apparatus further includes a detector (170) that photoelectrically detects the pattern image and generates a first output signal containing a representation of the image, and position detection system (174), electrically connected to the detector, that detects a position of the pattern based on the first output signal, and determines a deviation of the position from an ideal position. The position detection system then generates a second output signal containing deviation information representing the deviation. The apparatus further comprises a memory unit (M), electrically connected to the position detection system, that stores the deviation information contained in the second output signal. Further included in apparatus 100 is a correction process unit (B), electrically connected to the memory unit, that generates a correction value for eliminating the deviation based on the deviation information.