A sheet feeding apparatus with a buffer system is disclosed, in which a sheet feeding drum has a certain rotational speed regardless of the size of the sheet to feed a plurality of sheets to a sheet finisher and eject the sheets after exactly aligning them. The sheet feeding apparatus includes sheet feeding grips 36a, 36b, 36c and 36d provided on the outside of a sheet feeding drum 105 at certain intervals, and a sheet feeding grip controller (cam) 42 allowing the sheet feeding grips to selectively grip the sheets moving through the outside of the sheet feeding drum 105. The sheets gripped by the sheet feeding grips are buffered by the end fence and are ejected to a sheet finisher through a sheet ejection path when the end fence is opened. The sheet feeding drum 105 includes a plurality of support rings 33a, 33b, 33c, and 33d arranged at certain intervals, sheet feeding rollers 34a, 34b, 34c and 34d respectively formed among the support rings, and a central shaft 35 fixing the support rings and the rollers, the sheet feeding grips being provided in the support rings.