A door moving apparatus includes a motor unit, a first gear, a second gear, an endless belt, a drum, and a rotator. The first gear is mounted on a rotary shaft of the motor unit. The second gear includes a diameter larger than a diameter of the first gear and teeth more than the first gear. The endless belt passes over the first gear and the second gear. A rotary power of the second gear is transmitted to the drum via a rotary power transmission mechanism. The rotator is configured to reduce a separation of the endless belt from a preset running path.