Automatic document feeder and image reader

1. Field of the Invention The invention provides an image reader provided with an automatic document feeder which has a switchback path and can perform a both-faces processing operation, and which makes it possible to simplify the control of a switchback operation and handle a long-sized document sheet without making the diameter of a feed roller large and making the switchback path unnecessarily long. An automatic document feeder of the invention comprises a feed path for feeding a document sheet drawn out from a paper feed stacker to an image reading portion facing a feed roller, a switchback path c for making a document sheet which has been processed at the image reading portion switchback, a pair of switchback rollers which are provided so as to make a document sheet switchback in the switchback path and are able to turn forward and backward, and a paper discharge path for discharging a document sheet being in the switchback path onto a paper discharge stacker. Here, the switchback path c is provided in a casing below the paper discharge stacker and the casing has an opening formed in it so that the fore end of a document sheet guided into the switchback path projects from the casing. Further, the pair of switchback rollers are disposed at the downstream side in the switchback path so that the fore end and the rear end of a document made to switchback do not overlap each other through the feed roller.