A belt driving device and associated method are provided. The driving device includes a plurality of rollers including a driving roller. A belt is configured to be tensioned by the plurality of rollers, and to be driven by the driving roller. An outside roller is configured to contact an outer surface of the belt and to be driven by a driving source. A detection portion is configured to detect a driving load of one of the driving roller and the outside roller. A controller is configured to drive the other one of the driving roller and the outside roller based on the driving load detected by the detection portion.