A corrugated fiberboard feeding apparatus comprising: an upstream transporting unit that has a plurality of ejection rollers which eject a corrugated fiberboard placed on upper surfaces thereof, and transports the corrugated fiberboard placed on the ejection rollers; and a downstream transporting unit that is adjacent to a downstream side in a sheet transfer direction with respect to the upstream transporting unit and transports the corrugated fiberboard ejected from the upstream transporting unit to a sheet processing unit on the downstream side, wherein the downstream transporting unit has a downstream suction unit that has an opening facing a sheet transport passage, and a feed roller that is accommodated in the downstream suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, wherein the corrugated fiberboard feeding apparatus has an upstream suction unit on an upstream side of the downstream suction unit, characterized in that the downstream suction unit further comprises an auxiliary suction unit that is disposed on the downstream side of the downstream suction unit and has an opening facing the sheet transport passage, and a feed roller that is accommodated in the auxiliary suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, and a distance in the sheet transfer direction between a downstream end of the opening of the downstream suction unit in the sheet transfer direction and an axis of the ejection roller on the most downstream side in the sheet transfer direction, out of the plurality of ejection rollers, is set to a maximum distance of a mutual distance between a plurality of transport rollers of the sheet processing unit, which transport the corrugated fiberboard, or shorter, and further in that an adjusting means for adjusting suction power is included in each of the upstream suction unit, the downstream suction unit, and the auxiliary suction unit. an upstream transporting unit that has a plurality of ejection rollers which eject a corrugated fiberboard placed on upper surfaces thereof, and transports the corrugated fiberboard placed on the ejection rollers; and a downstream transporting unit that is adjacent to a downstream side in a sheet transfer direction with respect to the upstream transporting unit and transports the corrugated fiberboard ejected from the upstream transporting unit to a sheet processing unit on the downstream side, wherein the downstream transporting unit has a downstream suction unit that has an opening facing a sheet transport passage, and a feed roller that is accommodated in the downstream suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, wherein the corrugated fiberboard feeding apparatus has an upstream suction unit on an upstream side of the downstream suction unit, a downstream suction unit that has an opening facing a sheet transport passage, and a feed roller that is accommodated in the downstream suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, wherein the corrugated fiberboard feeding apparatus has an upstream suction unit on an upstream side of the downstream suction unit, characterized in that the downstream suction unit further comprises an auxiliary suction unit that is disposed on the downstream side of the downstream suction unit and has an opening facing the sheet transport passage, and a feed roller that is accommodated in the auxiliary suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, and an auxiliary suction unit that is disposed on the downstream side of the downstream suction unit and has an opening facing the sheet transport passage, and a feed roller that is accommodated in the auxiliary suction unit and has an outer circumferential surface of which a part protrudes to a sheet transport passage, and a distance in the sheet transfer direction between a downstream end of the opening of the downstream suction unit in the sheet transfer direction and an axis of the ejection roller on the most downstream side in the sheet transfer direction, out of the plurality of ejection rollers, is set to a maximum distance of a mutual distance between a plurality of transport rollers of the sheet processing unit, which transport the corrugated fiberboard, or shorter, and further in that an adjusting means for adjusting suction power is included in each of the upstream suction unit, the downstream suction unit, and the auxiliary suction unit.