To provide a sheet processing device and an image forming system which can finely crimp a bundle of sheets.

A sheet processing device includes: a work part for providing a hole 5a in a sheet 5; a control part which controls the work part and provides the hole 5a in one or more sheets of three or more sheets; a bundling part which stacks the three or more sheets to form a sheet bundle 6; and a sheet binding part which crimps overlapping parts 5b overlapped on the hole 5a on each other in a direction of overlapping the sheets 5 in the sheet bundle 6 to bind the sheet bundle 6.