To provide a post-processing device which can secure versatility by reducing the dependence on the configuration of the connection thereof between the upstream and downstream sides when a plurality of post-processing devices are connected for use and which is increased in reliability, and also provide a post-processing system, an image forming device, and an image forming system.

This post-processing device used by connecting at least one or more of the devices includes at least one or more communication parts for communicating with any of the other devices connected to the upstream side and the downstream side, a control unit for controlling the post-processing device, and at least one or more post-processing parts for post-processing a recording medium. The control unit edits the information on the processed state of each recording medium based on the post-processing performed by the post-processing part of the post-processing device. The communication part transmits the information on the processed state edited by the control unit to the devices on the downstream side.