1. An image sensing apparatus, comprising: synthesis target information storage means for storing data representing a synthesis target image and photographic conditions prevailing at time of photography of the synthesis target image; image sensing means for photographing background and outputting data representing a background image; image adjustment processing means for applying image adjustment processing for at least one of a color adjustment and a luminance adjustment to a synthesis target image represented by synthesis target image data, which has been stored in said synthesis target information storage means, based upon the photographic conditions of the synthesis target image that have been stored in said synthesis target information storage means and photographic conditions of the background image sensed by said image sensing means; and image synthesis means for combining the synthesis target image data that has been subjected to the image adjustment processing by said image adjustment processing means with the background image data output from said image sensing means, and outputting composite image data representing a composite image.