PURPOSE: To optimize the transport of a print product by detecting the positions of the leading/trailing edges of a printed matter, inspecting whether it exists in a prescribed monitoring area or not, and controlling the transport speed.

CONSTITUTION: A folding product in a folding device is guided by transport belts 3-6 from a cylinder 2 and the cylinder 2 is rotated by a motor 9 through a gear transmission device 8. The transport belts 3-6 are driven by the motor 9 through the gear transmission device 8 and a driving belt 10. The motor 9 is controlled by controller 12 based on the outputs of a scanning detector 7 and an angle oscillator 11. A monitoring area against the leading and trailing edges of a printed matter, an area where the printed matter does not exist and a printed matter area are set to the prescribed number of printed matters 1 at the time of control. It is inspected whether the trailing edge position exists in the monitoring area or not, the dispersion of the value is monitored and transport speed is controlled.