1. An image-capturing device, comprising: a plurality of micro-lenses disposed in a two-dimensional pattern near a focal plane of an image forming optical system; an image sensor that includes a two-dimensional array of element groups each corresponding to one of the micro-lenses and made up with a plurality of photoelectric conversion elements which receive, via the micro-lenses light fluxes from a subject having passed through the photographic optical system and output image signals; and a synthesizing unit that combines the image signals output from the plurality of photoelectric conversion elements based upon information so as to generate synthetic image data in correspondence to a plurality of image forming areas present on a given image forming plane of the image forming optical system, the information specifying positions of the photoelectric conversion elements output image signals that are to be used for generating synthetic image data for each image forming area.