The method includes divisionally-capturing a target region from a platform such as an airplane (1) by rendering viewing angles as being different from each other as well as rendering a focal length (f, f′) as being different with reference to a predetermined ground resolution, thereafter generating an elevation model (5) of the entire target region (1) in accordance with matching of elevation models (3, 3) generated based on respective divisionally-captured images (2) between image capturing overlap regions (4), and generating an orthophoto image of the entire target region by applying an orthogonal projection transformation processing to the respective divisionally-captured images (2) by use of altitude information of the elevation model (5).