A belt driving device including a rotatable seamless belt wound around rotatable driven rollers and one or multiple rollers, and a driven roller unit including the rotatable driven rollers. The driven roller unit includes a detection roller rotatably driven, a surface of which contacts an inner surface of the belt to slide in a direction of a rotary shaft thereof when shifting occurs on the belt in a width direction thereof; a correction roller rotatably driven, a rotary shaft of which is rotatably supported to displace around any single point on the rotary shaft thereof while a surface thereof contacts the inner surface of the belt; and a conversion unit to convert displacement of the detection roller in the direction of the rotary shaft of the detection roller into angular displacement of the correction roller in a direction of rotation of the correction roller.