A plurality of image processing units (7a, 7b, 7c) are provided for respective groups formed by division into groups of a plurality of images the order of which is continuous when images respectively having overlapping portions corresponding to the same portion of a subject are arranged so as to be adjacent to each other, and concurrently perform processing for detecting combination position information for combining an image in a group and an image adjacent to the image without a positional displacement by image matching. Combination information transfer paths (10a, 10b) respectively transfer, between the image processing units (7a, 7b) and between the image processing units (7b, 7c), the combination position information between two images belonging to different groups.