1. A method for detecting a position of a prescribed pattern in an information recording image that contains the prescribed pattern, comprising the steps of: (a) detecting a rough position of the prescribed pattern in the information recording image in units of pixel size; and (b) detecting a detailed position of the prescribed pattern in the information recording image in units less than the pixel size, according to the rough position detected by the step (a) and a center of gravity of a distribution of similarities between regions in the information recording image and a reference image of the prescribed pattern.