A sheet processing apparatus includes a sheet conveyance passage, a sheet circulation passage, a first conveyor, a second conveyor, a third conveyor, and circuitry. In the sheet circulation passage, a sheet is circulated to be overlaid with a following sheet in the sheet conveyance passage. The circuitry circulates the sheet in the sheet circulation passage to overlay the sheet with the following sheet conveyed after the sheet in the first sheet conveyance passage, at an upstream position of the first sheet conveyance passage, and adjusts a sheet conveyance speed of the third conveyor to circulate the sheet, based on a reduction amount that is obtained when a preceding amount of a leading end of the following sheet with respect to a leading end of the sheet is reduced while the following sheet is temporarily stopped due to a temporary stop of the first conveyor.