PROBLEM TO BE SOLVED: To miniaturize a relay unit post-assembled in the in-body paper discharge space of an image forming device.SOLUTION: This relay unit 5 includes a lower guide member 51 which is post-assembled in the in-body space of the in-body paper discharge type image forming device and which forms a lower guide surface and an upper guide member 52 which is rotatably attached to the lower guide member and which forms an upper guide surface. The lower guide member 51 and the upper guide member 52 are connected to each other rotatably through hinge joint parts S. The hinge joint part S includes a rotating shaft 523 projecting from the second side surface of the upper guide member 52 rearward and a bearing part 591 which projects, downward, from the surfaces 59A of the support member 59 facing the rotating shaft and which receives the rotating shaft 523. The hinge joint parts S are disposed in a maximum sheet conveying area 50A.