A folding machine folding a sheet P1 into a predetermined folding pattern to form a signature P3, a saddle stitching machine 3 arranged downstream of the folding machine to staple and fold the signature and a control unit 15 controlling the folding machine and saddle stitching machine are provided. The folding machine has parameters adjustable depending on a thickness of the sheet. The saddle stitching machine has parameters adjustable depending on a thickness of the signature P3, P4. The control unit sets the parameters of the folding machine based on the information about the thickness of the sheet and sets the parameters of the saddle stitching machine based on the information about the thickness of the signature calculated using the information about the thickness of the sheet and the information about the folding pattern of the folding machine.