A two-sided reading-out apparatus and an image forming apparatus including the two-sided reading-out apparatus are capable of simplifying processing at a time of reading out the image respectively for one-side surface reading-out and two-side surface reading-out in an original document, preventing the large-sizing of the apparatus, and avoiding the cost run-up thereof, thereby securing optimum productivity. A first document conveying path extends from a document stand to a contact glass and a second document conveying path extends from the contact glass to a document discharging tray via a fixed reading-out section. The direction of conveying the document is changed over by a changing-over claw. Thus, the image data on the front and rear sides of both surfaces of the document can be read out without being overlapped.