An image-forming system is composed of an image-forming apparatus body, a folding device, a bookbinding device, and a finisher, which are connected to the image-forming apparatus body. In the image-forming system, in order to support maintenance, an available period of time for maintenance for each processing module (a unit or a device sectionalized in a processing functional unit) is calculated based on contents of a job presently in execution and contents of registered jobs so as to display the available period of time for maintenance of the calculated processing module on an operation display.