In the present invention, traffic information broadcast by a traffic information center is received, indexes are created, and the index and travel speed information on a mobile object are stored. A matching table is created to match first map data for use in broadcasting the traffic information and second map data used by a navigation system to each other. The traffic information is simply matched to the second map data used by the navigation system, using the created matching table. When the travel speed of the mobile object on each link is intended to be displayed with a predetermined color after the matching of the traffic information to the second map data, the storage capacity of a traffic information storage unit is reduced, which stores traffic information displayed together with arrows for indicating the travel direction.