A sheet finisher of the invention includes a saddle stitch unit configured to stitch a center of a sheet bundle in which printed sheets are bundled, a fold unit configured to fold the center stitched by the saddle stitch unit and to form a fold line, a fold reinforcing unit that includes a reinforce roller, moves the reinforce roller along a direction of the fold line while applying pressure by the reinforce roller to the fold line of the sheet bundle transported from the fold unit, and reinforces the fold line, and a control unit configured to transport the sheet bundle from the fold unit to the fold reinforcing unit and to control to stop the fold line of the sheet bundle at a position of the reinforce roller, and the control unit changes, according to a thickness of the sheet bundle, a transport distance from a specified position in the fold reinforcing unit to the position where the sheet bundle is stopped.