Disclosed is a technology that specifies each of a plurality of two-dimensional codes in an image and reduces the processing time for judging color in each cell region in each specified two-dimensional code. Based on edge images generated from obtained images, candidate regions among these edge images are extracted, a judgment is made about whether or not a characteristic pattern is included in each of the corresponding regions in the original images that correspond to these extracted candidate regions, and then the two-dimensional code regions are detected from among the original images. The color is judged both for each pixel group that comprises each row of that region and for each pixel cell, in pixel array order. If it is determined that a certain number or more pixels in each row that corresponds to each cell region are included in the color judgment region, color judgment is omitted for the remaining pixels in that row.