A sheet processing apparatus includes a sheet holding unit, a sheet conveying unit configured to convey a plurality of sheets one by one onto the sheet holding unit during sheet processing, wherein the plurality of sheets includes a first sheet and a second sheet that is conveyed immediately after the first sheet, an adhesive applying unit configured to apply an adhesive material on the first sheet held on the sheet holding unit before the second sheet is conveyed onto the first sheet, and a pressing unit configured to press the second sheet against the first sheet after the second sheet is conveyed onto the first sheet.