PURPOSE: To make a paper folding slip preventable, by setting nip pressure between first and second rollers so strong as a degree capable of making paper to be inserted into space between second and third rollers after both ends in and around the feed direction side of the paper.

CONSTITUTION: In a state that nip pressure between first and second rollers 11 and 12 produced by a spring 21 is set at a pressure point P1 and being skewed, even when paper 17 is fed to the side of a chute 14 and one end of a feed direction side face 17a reaches to a bottom part of the chute 14, this nip pressure P1 is not so large to the extent of partially bending the paper 17 so that the paper 17 is no longer inserted into space between second and third rollers 12 and 13. During a while, the other end of the side face 17a reaches to the bottom part of the chute 14 whereby a skew in the paper 17 is corrected. At this time, both ends of the side face 17a of the paper 17 are detected by sensors 15 and 15, and since the nip pressure between these first and second rollers 11 and 12 is set to a pressure point P2, the paper 17 is largely bent in a partial manner and therefore inserted into space between these second and third rollers 12 and 13, thus the paper is correctly folded up.