A sheet post-processing device includes a tray, an evacuating member, a regulating member mounted on the tray, and a feed mechanism. The tray can receive sheets thereon. The evacuating member temporarily evacuates, from a conveyance path, sheets being conveyed, stacks the evacuated sheets into a pile, and conveys the pile of sheets onto the tray through the conveyance path. The feed mechanism includes a spongy elastic member and moves the pile of sheets along the tray toward the regulating member. When stacking three or more sheets into a pile, the evacuating member performs the stacking such that, in the pile conveyed to the tray, an edge of each intermediate sheet protrudes toward the regulating member beyond an edge of an uppermost sheet and an edge of a lowermost sheet.