Abstract: A document feeder having a transportation belt unit for transporting a document original; a front side plate and a rear side plate respectively projecting upright at widthwise opposite edges of the transportation belt unit; a pair of stays each extending between the front side plate and the rear side plate; a front stay plate detachably fastened to portions of the pair of stays adjacent to the front side plate by means of a front fastening member; and a rear stay plate fastened to portions of the pair of stays adjacent to the rear side plate by means of a rear fastening member which can be loosened. The front side plate has a recess open to its underside for receiving the front stay plate for engagement therewith in a disengageable manner. The front stay plate is fastened to the front side plate in engagement with the recess by the front fastening member.