A position detecting method detects each position of a photosensitive substrate when executing shots of circuit patterns so that the circuit patterns are further superposed on the photosensitive substrate already formed with the circuit patterns. The method comprises the steps of performing a shot of a circuit pattern of a reticle in superposition on liquid crystal pixel segments already formed on a glass plate, registering, in a memory, a circuit pattern as a reference image in the liquid crystal pixel segment and performing pattern matching with other fields of the liquid crystal pixel segments by use of this reference image. An alignment is conducted based on a position of circuit pattern extracted thereby.