A post-processing device includes a processing tray, an aligning plate, a transport section, a feeding section, and a pressing section. A sheet before being subjected to stapling processing by a stapler is to be mounted on the processing tray. The aligning plate aligns ends of a plurality of sheets. The transport section transports the sheet toward the aligning plate. The feeding section is provided between the transport section and the aligning plate and feeds the sheet in a transport direction. The pressing section is provided between the transport section and the aligning plate and applies, to the sheet, a pressing force having a component in a direction opposite from the transport direction. Further, the pressing section applies the pressing force to the sheet before the feeding section applies a feeding force to the sheet.