A replaceable stack sheet replaceably provided in a medium integration/separation device to guide integration of a medium according to an embodiment includes a body which is coupled to a rotary shaft and in which a plurality of support shafts are spaced apart from each other in a circumferential direction, and a plurality of sheet pieces having ends rotatably coupled to the plurality of support shafts.

A sheet feeding apparatus includes a sheet conveying unit configured to convey a sheet along a conveyance path, a detecting unit configured to detect the sheet passing along the conveyance path, a control unit configured to determine an amount of delay of a sheet conveyed along the conveyance path based on the detection and determine information to be output based on the amount of the delay, and an output unit configured to output the information.