PROBLEM TO BE SOLVED: To suppress an adhesion defect which may occur when the rotation of a step roll is decelerated from a steady operation and then increased again. SOLUTION: A control unit 65 of a corrugated cardboard sheet manufacturing apparatus 10 is a deceleration operation in which a step roll 17A is decelerated to a second set speed V2 during a steady operation in which the step roll 17A is rotated at a first set speed V1. After executing the above, it is possible to execute the speed-increasing operation in which the stage roll 17A is accelerated to the third set speed V3. In steady operation, the on-off valve 60A is closed, and the pressure adjusting valve 55 supplies steam to the introduction unit 17b at the first set pressure P1. In the deceleration operation, the state of the on-off valve 60A and the pressure adjusting valve 55 is maintained. In the speed-increasing operation, the on-off valve 60A is switched from the closed state to the open state, and the pressure adjusting valve 55 is adjusted so that steam is supplied to the hollow portion 17b at the second set pressure P2. [Selection diagram] Fig. 3
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