A post-processing device include a conveyed medium stacking portion, a medium bundle stapling member, a medium bundle stacking portion and a medium bundle stacking control unit. A plurality of recording mediums, on which images are recorded, are conveyed and stacked into the conveyed medium stacking portion. The medium bundle stapling member staples a medium bundle, which is a bundle of the plurality of recording mediums stacked on the conveyed medium stacking portion, with staples. The stapled medium bundle is conveyed and stacked into the medium bundle stacking portion. The medium bundle stacking control unit stacks a second medium bundle on a first medium bundle under the condition that a second stacking stapling position deviates from a first stacking stapling position in a width direction by a distance not less than a staple width.