A navigation system includes: a map information acquiring unit 31 for acquiring map information; an HOV lane decision unit 38 for deciding whether an HOV lane is included in a road represented by the map information acquired by the map information acquiring unit 31 or not; a road number processing unit 43 for performing, when the HOV lane decision unit 38 decides that the HOV lane is included, processing of adding information representing the HOV lane to a road number of the road including the HOV lane; and a display processing unit 44 or a voice information unit 46 for causing the road number passing through the processing by the road number processing unit 43 to be displayed on the guide map or output in voice.