A first storage unit is a storage area for storing original images. Inputted to an input unit is an operation instruction from a user. An obtaining identifying unit identifies an optimal original image pair. An obtaining processing unit accesses the first storage unit to obtain the optimal original image pair. A converting unit converts scales of respective images included in the optimal original image pair into a designated scale to generate intermediate images. A corresponding point matching unit makes the corresponding areas of the intermediate images coincide. A combining unit combines the intermediate images using a predetermined ratio to generate a target image. The resultant target image is outputted from an output unit to a monitor.