To provide a paper folding performance inexpensively in a stable condition in a paper post-processing device that carries paper after printing from a printer, performs continuous paper folding, cuts it every job, offsets paper after the cut, and repeats the folding.

The paper post-processing device comprises feeding holes at both ends in a conveying direction, a tractor for conveying the paper after printing from the printer that has a folding sewing machine in the rectangular direction to the feeding holes and uses continuous paper, a cut part capable of performing the paper cut at a folding sewing machine position, a swing fin that reciprocatively turns and sorts it in the front and back directions with the folding sewing machine, paddles for interfering with, pressing, and regulating both ends of the folding sewing machine, and a table for loading paper folded by the folding sewing machine. In a stage where paper is continuously folded or in a stage where paper is cut by the paper folding sewing machine and the paper per cut is offset and folded in the paper width direction, the paddles are arranged at positions for always interfering with, pressing, and regulating both ends of the paper folding sewing machine.