A sheet sorter includes a sheet discharge tray, a sheet conveyance unit, and a sheet pressing guide. The sheet conveyance unit is configured to convey sheets in a conveyance direction and configured to be shifted in a shift direction along a sheet plane and in a shift direction that intersects the conveyance direction, so as to sort the sheets loaded onto the sheet discharge tray from the sheet conveyance unit. The sheet pressing guide is configured to contact and press the sheets, configured to move together with the sheet conveyance unit in conjunction with the sheet conveyance unit moving in the shift direction, and configured to contact a topmost sheet among the sheets loaded on the sheet discharge tray only at a downstream edge of the topmost sheet in the conveyance direction.