1. An image data output apparatus for outputting image data representative of a single image through a conversion into image data representative of partial images each to be recorded, when the single image is outputted on a divisional basis into a plurality of sheets, on the associated sheet, said image data output apparatus comprising: a partial image designation section for designating a desired partial image of partial images to be outputted to the plurality of sheets in accordance with an operation, said partial images constituting the single image; and a data output section for outputting image data representative of the partial image designated by said partial image designation section, of the single image.