1. An image combining system comprising: an imager device for dividing a subject into a plurality of partial images, and photographing the partial images; a conversion parameter estimation unit for estimating a geometric conversion required for a combination between the partial images, and calculating image conversion parameters for the geometric conversion; a storage unit for storing the partial images and the calculated image conversion parameters corresponding to the partial images; an image combination data retrieval unit for selecting partial images required for generating a mosaic image, and retrieving the selected partial images and image conversion parameters corresponding thereto from said storage unit, respectively; an image combination unit for geometrically converting photographed partial images on the basis of a current partial image using the partial images and image conversion parameters retrieved by said image combination data retrieval unit, combining them to generate a mosaic image, and generating image data for displaying the current partial image and at least part of the mosaic image; and a display device for displaying an image in accordance with the image data generated by said image combination unit.