To provide a roller driving mechanism capable of sufficiently suppressing occurrence of noise by backlash.

An O-ring 81 is engaged with a disk part 69 formed integrally with a roller gear 61, and is connected by pressure to a sleeve 73 formed integrally with a small diameter part 72 of an intermediate gear by elastic deformation. Therefore, not only a driving force by fitting of the small diameter part 72 to the roller gear 61 but also a driving force by rolling friction between a sleeve 73 and the O-ring 81 is transmitted to a conveying roller. The pressure connection part is disposed inside a pitch circle of the small diameter part 72, the driving force by the rolling friction is transmitted at a reduction gear ratio lower than that for the driving force by the fitting. A restoring force F of the O-ring 81 always connects by pressure a flank on the front side of the small diameter part 72 in the rotation direction to a flank on the back side of the roller gear 61 in the rotation direction.