The invention provides an automatic document feeder, an image reading apparatus and an image forming apparatus which is low in costs and small in size, comprising: a motor 102 configured to continuously drive the document conveyance unit 32 for separating the original documents from original station 24 to feed, and a motor 103 configured to drive read-in rollers pair 37 for transferring documentsseparated and fed by the document conveyance unit 32 to reading position 80, and a motor 104 configured to drive invert rollers pair 45 for discharging original documents transferred from the readingposition 80 to a document discharging plate 43; in the ADF23(automatic document feeder 23), the feeding motor 103, reading motor 103 and invert motor 104 are disposed in an approximately serial direction, in order to supply air via a fan motor 214 along arranging direction of the feeding motor 103, reading motor 103 and invert motor 104.