Patent ID: 7503886

Claim:
A paper folding device, comprising: a folding roller pair that folds a paper; a carry roller pair that feeds the paper to the folding roller pair; a first and second biasing device configured to switch a direction in which the paper is bent by the folding roller pair and folding in the paper; and a tension applying device that applies tension to the paper folded between the folding roller pair and the carry roller pair, wherein the biasing device applies a fixed tension to the paper, for carrying the paper the tension is used to bring the paper into contact with an upper side folding roller of the folding roller pair on a side where paper is folded, and the paper is folded in a nip of the folding rollers, wherein standby positions of opposing biasing devices function as paper guides so that the paper makes contact with the upper side folding rollers of the folding roller pair on the side where paper is folded, wherein the standby positions of the paper guides are configured to be shifted by a shifting device, and wherein the device for shifting shifts the positions in response to a paper thickness and/or a number of times of folding.