A sheet guiding rib protrudes below a sheet suction surface of a plurality of suction conveyer belts, the sheet guiding rib being provided at a position on a downstream side in a sheet conveying direction of a sheet suction region, in which a sheet can be sucked, of the sheet suction surface of the plurality of suction conveyer belts, and between the plurality of suction conveyer belts. At a time of conveying a topmost sheet sucked and deflected downward at a part of pressing a sheet surface detecting flag, a deflection amount of the topmost sheet is reduced by bringing the deflected part of the topmost sheet into abutment against the sheet guiding rib.