Patent ID: 8087654

Claim:
A post-processing device comprising: a conveyed medium stacking portion into which a plurality of recording mediums, on which images are recorded, are conveyed and stacked; a medium bundle stapling member that staples a medium bundle with staples for saddle stapling processing in which a central portion of the medium bundle in a conveyance direction of the medium bundle is stapled, the medium bundle being a bundle of the plurality of recording mediums stacked on the conveyed medium stacking portion, wherein the medium bundle stapling member comprises: movement stacking portions that support the central portion of the medium bundle in the conveyance direction of the medium bundle; staple driving portions that drive the staples for stapling the central portion of the medium bundle in the conveyance direction of the medium bundle; and staple bending portions that bend tips of the driven staples; a medium bundle stacking portion that stacks the stapled medium bundle thereon, wherein the medium bundle stacking portion is located directly under the medium bundle stapling member so that the stapled medium bundle drops in a vertical direction from a supporting position at which the medium bundle is supported by the medium bundle stapling member; and a medium bundle stacking control unit that 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, wherein the first medium bundle indicates the medium bundle stacked in the medium bundle stacking portion, the second medium bundle indicates the medium bundle conveyed to and stacked on the medium bundle stacking portion after the first medium bundle is stacked on the medium bundle stacking portion, the first stacking stapling position indicates positions of the staples in the first medium bundle stacked in the medium bundle stacking portion, the second stacking stapling position indicates positions of the staples in the second medium bundle stacked in the medium bundle stacking portion, and the staple width indicates a width of the staple in the width direction of the medium bundle perpendicular to a conveyance direction of the medium bundle.