Automatic document feeder and image reader

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 a, b for feeding a document sheet drawn out from a paper feed stacker to an image reading portion facing a feed roller 5, a switchback path c for making a document sheet which has been processed at the image reading portion X switchback, a pair of switchback rollers 25 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 d for discharging a document sheet being in the switchback path c onto a paper discharge stacker 4. Here, the switchback path c is provided in a casing below the paper discharge stacker and the casing has an opening 1 p 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 c so that the fore end and the rear end of a document made to switchback do not overlap each other through the feed roller 5.