A device for driving a rear wheel of an electric vehicle is provided. In one embodiment, the rear wheel driving device includes a motor for supplying rotational power, a gear group connected to a rotor of the motor, a final gear connected to the gear group, an output shaft connected to the final gear and rotating, a hub installed on an outer circumferential surface of the output shaft using a nut, a wheel connected to the hub, an axle housing connected to the hub using a hub bearing, a motor cover protecting the motor and mounting an output shaft bearing, and a trailing arm connected to the axle housing using an axle housing bolt and configured to mount the motor from an exterior side to an interior side of a vehicle.