A control device includes: a determination unit that determines a beginning original document to which a function that lays out a plurality of original documents onto a single sheet with predetermined number of original documents and forms an image is applied; a judgment unit that sequentially judges whether the original document is the object to be laid out onto a single sheet together with other original documents, starting with the beginning original document; an original document number determination unit that determines the number of original documents formed on a single sheet, that is within the predetermined number of original documents and does not make blank spaces, based on the number of original documents to which judgments by the judgment unit are done and judgment results of the judgment unit; and an image forming start unit that makes an image forming unit start to form the image based on the number of original documents determined by the original document number determination unit.