To accurately display identification in a multi-stage display mechanism for automatically switching the identification when sheet feeding units are heaped and installed.

When the sheet feeding units 11-14 are heaped up, input members 124 provided for the respective units moves and a stage number display part 121 is rotated by a display gear part 122 engaging with an input rack part 125 to suitably display the stage number. A positioning pin 140 is engaged with a recessed part 143a provided for a positioning rib 143, which fixes the position of the stage number display part 121 to suitably display.