1. An method of detecting a pattern in a pattern detecting apparatus, the apparatus comprising a table for fixing a substrate having a formed wiring pattern and an alignment mark, an imaging unit which images a predetermined point in said substrate, a signal processing unit which processes a video signal send by said imaging unit and a control unit which controls the action of said table, the method comprising steps of: imaging a first alignment mark as a reference by said imaging unit; registering a substantially whole alignment mark in said imaged first alignment mark and a part of alignment mark in said imaged first alignment mark; imaging a second alignment mark in said substrate to be inspected by said imaging unit; and detecting a position of said second mark from said imaged second alignment mark, based on any of said substantially whole alignment mark or at least a part of said imaged first alignment mark.