A belt driving apparatus includes an endless belt stretched around a driving roller that drives the belt, a receiving roller that receives an external force through the belt, driven rollers arranged upstream of the receiving roller and downstream of the driving roller in a rotational direction of the belt, at least one of the driven rollers being supported to be movable in radially inward and outward directions of the belt in accordance with a tension in the belt. A braking unit performs braking by pressing a frictional member against a rotational shaft of one of the driven rollers and generating a frictional force, and converts a displacement of the movably supported driven roller in the radially outward direction into a relative displacement between the rotational shaft and the frictional member, the displacement being caused when the external force is applied to the receiving roller so as to decelerate rotation thereof.