A paper feeder including a fixed guide disposed at one side of a paper feeding tray. The fixed guide functions as a standard of position adjustment of documents, and faces in an orthogonal direction against a document transporting direction. The documents are fed from the document feeding tray by a pick-up roller, separated into one-by-one and fed to the downstream by a document separator comprised of a separate roller and a retard roller. These pick-up roller, separate roller, retard roller are disposed within the smallest width size of the documents stacked on the document feeding tray. The documents fed to the downstream are fed to a reading unit by the feed roller mounted in the movable guide side located opposite to the standard line. After the image data of the document is read by the reading unit, the document is discharged to the paper discharging tray by an extra roller.