IMAGE PROCESSING DEVICE, IMAGE PROCESSING METHOD AND IMAGE PROCESSING PROGRAM

An image processing device that accumulatively generates a synthetic image by joining a first image, which is a single image or is constituted by a plurality of the images joined together, and a second image that is input, every time when the second image is input, the device comprising: a center-position obtainment portion (11) that obtains position information on a first center point being a center point of each of the images constituting the first image and position information on a second center point being a center point of the second image; and a synthetic image generation portion (12) that obtains the first center point of an image overlapping the second image among the images constituting the first image, and that joins the first image and the second image to generate the synthetic image, using perpendicular bisectors between the obtained first center points and the second center point as a joint between the first image and the second image, based on the obtained position information on the first center points and the obtained position information on the second center point.