A bottom plate 25 is formed so as to open and close over substantially the entire bottom side of a document transport device 2, which is provided on the top of an image forming device, the bottom face of the bottom plate 25 being a pressure face for pressing against a document. The bottom plate 25 can be swung around a pivot 25a, and engages with a document transport device main body 21 by way of a document transport path bottom member 21. One end of the document transport path bottom member 71 is swingably supported by the document transport device main body 21, and a pin 71a that is provided at the other end thereof slidably engages in a groove 25c in a side wall 25b that is provided on the swinging end of the bottom plate 25, so as to open together with the bottom plate 25.