1. An image combining device, comprising: a read unit, which includes: a transparent holder to hold a flat medium, a plurality of matching reference points marked in an edge region; and an image read section of flatbed type, to read said medium held in said transparent holder placed on a reading window, a size of said medium being larger than a size of said reading window, and to generate a plurality of partial images, each of which includes an image of a part of said medium and a part of the plurality of matching reference points, the matching reference points being arranged along a part of an edge of the image of the part of said medium; and a control unit, which combines said plurality of partial images based on the matching reference points included in said plurality of partial images, and generates a combined image including an image of said medium.