PURPOSE: To prevent the speed of a carried document from being fluctuated by providing a carrying means by the use of a belt member in a scanning part document carrying device and carrying the document in a state where it is pressed to the belt member in an automatic document feeder arranged in an image forming device.

CONSTITUTION: As for the automatic document feeder arranged at the upper part of the image forming device; the scanning part document carrying device 40 is arranged to carry the document, and the document is carried by the belt member 41 in the case of reading an image by a scanner arranged at the lower part of the platen 3. In the carrying device 40, the guiding means of the belt member 41 consists of a driving roller member 42, platen rollers 44 and 44a and an end roller 45 and constitutes a polygonal carrying path. Then, the carrying action is executed while keeping the carrying speed of the document by the belt member 41 constant.