To improve the quality of paper folding accuracy by preventing the paper feeding amounts from varying depending on the slip generated between a pair of conveying rollers and the paper and the folding length from varying depending on the deviation of timing of a deflection auxiliary member to contact with the paper.

The quality of paper folding accuracy is maintained by integrally providing a paper end detection sensor 6 on an end stopper 7 to keep the distance between the paper end detection sensor 6 and the end stopper 7 short so that the motion timing of a deflection auxiliary member 8 to the end position of the paper 4 becomes hard to deviate even if a slip is generated between a conveying route 5 and the paper 4.