1. A position detecting method comprising: allowing a target detecting unit to calculate, by a computer, according to sensitivity represented by an amount of change of a pixel value at the time when a target aligned with a goal position in image data at a pixel level is displaced by a displacement amount at a sub-pixel level, a coincidence evaluation value of the target on the basis of comparison of goal image data in a state in which the target is arranged and image data including images of the target; and detect positional deviation of the target with respect to the goal position on the basis of the calculated coincidence evaluation value.