A driving device includes a motor, and a gear housing secured to the motor. The gear housing accommodates reduction gears. Rotation of the motor is reduced by the reduction gears before being transmitted to an output shaft supported by the gear housing. A support cylinder extends from an outer surface of the gear housing to support the output shaft. A surrounding cylinder extends from the outer surface of the gear housing to surround the support cylinder. Reinforcing ribs are located between the support cylinder and the surrounding cylinder. Each reinforcing rib extends from a circumferential wall of the support cylinder such that the angle between the reinforcing rib and a normal line that intersects the circumferential wall form a predetermined angle. Each reinforcing rib has a radially inward end connected to the support cylinder and a radially outward end connected to the surrounding cylinder.