To provide an automatic document feeder and an image forming device having the document feeder, capable of reducing the size and cost in the device by smoothly and surely carrying a document, even if a carrying passage up to switching back again after switching back the document, is set to the length or less in the carrying direction of the document.

In this automatic document feeder 71, a torque limiter 19 limits torque applied to a driving shaft (a shaft of a reversal roller) 70 to torque for co-rotating the reversal roller 11a by frictional force with the document S when the switched back document S is carried by a carrier roller 5b. A one-way clutch 67 interlocks with a driven member 69 only when the driving shaft 79 reversely rotates, and stops reverse rotation of the driving shaft 79 by stopping rotation of the driven member 69 by abutting on the driven member 69 when a switching member 10 moves to a guide position A to a third carrying passage (a switchback carrying part) 33.