PROBLEM TO BE SOLVED: To provide a document transport device with which an operator is prevented from erroneously rotating a stamp unit during jam processing and during cleaning of a rear device and stamp replacement performance can be improved even in the document transport device with end face reference.SOLUTION: A document transport device includes: document loading means; separation feeding means; transport means; discharge means; and a transport device body for supporting them. The transport device body is supported by an image forming apparatus body so as to be freely opened/closed. The document transport device also includes: a stamp 59 which is arranged on a downstream side in a document transport direction rather than a reading position and stamps a read completion mark on a document which is read; and a stamp unit 55 which is movably supported by the transport device body and detachably supports the stamp 59. The transport device body is opened from the image forming apparatus body, and the stamp unit 55 is moved to a first direction and moved to a second direction which is a device operator side to attach/detach the stamp 59.