In one embodiment of the present invention, a sheet post-processing apparatus includes an ejection path that successively feed sheets each with an image found thereon from an ejection outlet. A processing tray is disposed under the ejection outlet to temporarily store sheets fed from the ejection path. A port processing unit performs post processing such as binding and punching. The post processing unit is located under the ejection path and is provided with a cooling fan that sends air toward the post processing unit.