A driving device for an image carrying member, e.g., a belt, is to be provided that causes no increase in size and cost of the device and sufficiently stabilizes the velocity of the image carrying member upon fluctuation in load, so as to suppress or prevent formation of an image defect referred to as so-called "banding". A rotating member is made in contact with at least one of a driving force transmitting member and an image carrying member, which are arranged in a driving force transmission path for transmitting the driving force to the image carrying member, and the rotating member rotates in contact with the driving force transmitting member or the image carrying member, and providing, upon occurring fluctuation in velocity of the driving force transmitting member or the image carrying member, a viscous effect that suppresses the fluctuation in velocity.