1. An image scanning apparatus with a preview function, the apparatus comprising: a scanning unit that scans a plurality of documents to obtain scanned images of the plurality of documents; a display unit; and a control unit that controls the display unit to display the scanned images of the plurality of documents as preview images of the plurality of documents, and controls the scanning unit to scan respective scanning regions of all of the plurality of documents to obtain scanned images of the scanning regions of the documents using one scan command, wherein the scanning regions are respectively designated for the plurality of documents on the displayed preview images of the plurality of documents.