A round baler is provided with a bale-forming chamber that is surrounded by a pressing apparatus in the form of a single pressing belt or several pressing belts arranged one next to the other, wherein the pressing apparatus contacts a roller that can be driven and freely co-rotating rollers, of which at least one pre-tensioned roller is loaded by pre-tensioning apparatus in the sense of tightening the pressing apparatus such that it pre-tensions the pre-tensioned roller more strongly the farther this roller moves in a direction for loosening the pressing apparatus. The two ends of the pre-tensioned roller are each pre-tensioned by the pre-tensioning apparatus and can move independently of each other.