An automatic document feeder conveys an original along a conveying path to an original reading section in an image processor. First and second registration rollers for abutting the conveyed original against their contact portions, and a guide plate for guiding the conveyance of the original to the registration rollers are arranged in the conveying path. The first registration roller includes a plurality of reversing rollers made of rubber for reversing the original along a reversing path, and the reversing rollers are arranged a predetermined distance away from each other along an axis of their supporting shaft. A side edge in the direction of conveyance of the guide plate is in such a comb shape that projections and non-projections are alternatively formed. Each of the projections is opposite to a region between the adjacent reversing rollers, and extends toward the downstream side of the contact portions in the direction of conveyance. Each of the non-projections is opposite to each of the reversing rollers, and is positioned on the upstream side of the contact portions in the direction of conveyance and is in close proximity to the contact portions.