A processing unit performs a postprocess for a sheet bunch on a processing tray. In a waiting transportation path, a subsequent sheet can wait while the postprocess is performed for the sheet bunch. If sheet transportation is suspended, a controller determines whether concurrent transportation is performed or not on the basis of whether there is the sheet bunch on the processing tray and whether there is the subsequent sheet in the waiting transportation path. In the concurrent transportation, when the sheet bunch is outputted through an ejection port, the controller transports the subsequent sheet to an output roller and causes the subsequent sheet to protrude from the ejection port such that the subsequent sheet partially overlaps the sheet bunch, and after a rear end of the sheet bunch passes through the ejection port, the controller reverses the output roller and transports the subsequent sheet to the processing tray.