A sheet processing apparatus includes a first sheet conveyance path, a second sheet conveyance path that branches from the first sheet conveyance path at a branch portion on the first sheet conveyance path and merges with the first sheet conveyance path at a merging portion, and a control unit. The control unit controls a guide unit so as to guide a first sheet conveyed first in the sheet bundle to be processed by a sheet processing unit to the second sheet conveyance path, and guide a second sheet following the first sheet to the first sheet conveyance path to merge the first and second sheets in an overlapping manner at the merging portion, and guide at least one of sheets following the second sheet among a plurality of sheets constituting the sheet bundle to the second sheet conveyance path.