Image processors are provided for respective groups formed by grouping of images, the order of which is sequential when images respectively having overlapping portions corresponding to the same portion of an object are arranged so as to be adjacent to each other, and concurrently perform processing to detect combining-position information for combining an image in a group and an image adjacent to the image without any positional displacement by image-matching. The combining-position information between images belonging to different groups is respectively transferred, via combination-information transferring paths, between the image processors and between the image processors.