A position detection method of detecting a position of a mark. The method includes steps of detecting light from the mark under a first detecting condition to obtain a position of the mark as a first position, detecting light from the mark under a second detecting condition different from the first detecting condition to obtain a position of the mark as a second position, obtaining previously prepared data for relating a difference between the first and second positions to offset data for offsetting one of the first and second positions, and detecting the position of the mark based on the first and second positions and the previously prepared data.