To reduce the number of stop times of a stapling operation of a stapler by concurrently performing switching between storage boxes for housing staple wastes and switching between trays.

A sheet processing device includes a stapler 50, a cutter 151 which cuts off a surplus part of a staple which becomes redundant for a sheet bundle, a movable staple waste box 51 which moves integrally with the stapler and houses a cut-off surplus part of the staple as the staple waste and ejects it, a fixed staple waste box 60 which is provided at a home position of the stapler and houses the staple waste ejected from the movable staple waste box 51, and upper and lower loading trays 41 and 40 for loading the stapled sheet bundle. The sheet processing device ejects the staple waste to the fixed staple waste box from the movable staple waste box upon completion of switching between the upper and lower loading trays 41 and 40.