In a two dimensional image recording and reproducing scheme, a position of a prescribed pattern in an information recording image that contains the prescribed pattern is detected by detecting a rough position of the prescribed pattern in the information recording image in units of pixel size, and then 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 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.