To provide a sheet aligning device and an image forming system which are capable of improving the aligning performance and improving the capacity corresponding to sheets at low cost, and which meet the various market needs.

A multistage bin 12 is provided vertically in a sheet after- treating device, and a jogger 13 is provided so that it passes through the bin 12. The jogger 13 is structured to be moved across the width of the bin 12, or across the width of the sheet, and the jogger 13 is pressed against one end face of the sheets to move the sheets across the width, while the other end face of the sheets is pressed against a aligning reference plate on opposite side. Then, the jogger is further excess-fed and then is returned to align the sheets. At this time, the jogger 13 is not driven uniformly, but it is most suitably driven to align the sheets based on various information on the sheets.