PURPOSE: To enhance the sheets accommodating ability by giving each sheet undulated curl prior to feed into the sheet folder, in case sheets shall be sent through a sheet folder to be accommodated in an exhaust tray or the like, and thereby providing possibility of placing the sheets neatly when they are folded.

CONSTITUTION: Each sheet 29a after copying in a copying machine is sent to a curling device 11 through a guide 27, and when has reached immediately before rolls 12, 15, it is sensed by a sensor 25, and the signal thus emitted will actuate a timer of a control device 26 so as to deenergize a solenoid 22. Now a rod 23 and a pair of rolls for curling 18, 19 are elevated by a spring 24. The sheet 29a is transported being pinched by belts 14, 17, and when the half of it has passed, the above-mentioned timer of control device 26 is put off. Thereby the rolls 18, 19 are sunk to give the sheet 29a such a curl that the front and back halves are directed oppositely to each other. In this attitude held, the sheet is exhausted from a guide 28.