PURPOSE: To enable a sheet to be always reliably turned over, by a method wherein, in a device which is provided with a turn-over route being branched at and connected to a part halfway along a sheet conveyance route and returns a sheet, guided to the turn-over route, to the sheet conveyance route, a suction means is mounted to a turn-over branching part.

CONSTITUTION: A sheet turning-over device is provided with a main turn-over roller 5, located on the side of a sheet conveyance route, and turn-over rollers 6 and 7 on the convey-in and convey-out side, which are positioned facing the main turn-over roller 5 with the sheet conveyance route therebetween, located up and down the conveying direction, and are rotated in a driven manner by means of the main turn-over roller 5. The turn-over roller 6 and 7 are positioned in a stagger position relation therebetween and the two rollers 6 and 7 make contact with or are separable from each other. A turn-over route 9, passing between the two rollers 6 and 7, is branched from a sheet conveyance route 4. In which case, a feeler 15 for detecting the rear end of the sheet is movable in and out from the nip part formed by the rollers 5 and 6, and a suction means 16 is located to a portion on the convey-out side of the lower part the turn-over route 9 to control operation according to the output of the feeler 15.