There is provided a navigation system which enables efficient driving in a lane where advancing or leaving relative to other lanes of the road is restricted, such as for a carpool lane. Map data including road information regarding advancing/leaving points in a road having a carpool lane is read from a DVD 2, and stored in a data buffer 10. A route search processing section 32 used the map data stored in the data buffer 10 to perform route search processing, taking the availability of the carpool lane into consideration. When route guidance using the carpool lane is performed, a carpool lane guide section 18 performs predetermined lane change guidance visually and/or orally, at a timing when the advancing/leaving point at which the route is to be changed approaches within a predetermined distance from the position of the vehicle.