A sheet processing apparatus sandwiches a sheet media in a two-ply sheet in which two sheets are overlaid and bonded together at a portion of the two-ply sheet. The sheet processing apparatus includes a fixing device, a tray, and a roller. The fixing device applies heat and pressure to the two-ply sheet. The tray is disposed downstream from the fixing device in a conveyance direction of the two-ply sheet, to stack the two-ply sheet. The roller conveys the two-ply sheet vertically downward toward the tray after the two-ply sheet passes through the fixing device.