An automatic document feeder (ADF) for use with an electrophotographic copier, digital copier or similar image recorder for selectively feeding ordinary documents in the form of separate sheets and a continuous document in the form of computer form (CF) paper. Sprocket holes formed through the CF paper are sensed to controllably transport and stop the CF paper on the basis of the number of sensed holes. Slippage of the CF paper apt to occur when the paper begins to be transported and when it is transported by a belt that faces a glass platen is prevented from being erroneously determined to be a jam. Cuts intervening between nearby sprocket holes for temporarily fastening a carbon to the CF paper are prevented from being sensed as the sprocket holes.