An apparatus includes a map information storage section (16) for storing map information on an area by area basis formed in meshes; a positioning section (15) for measuring its own present location; a new road detecting section (19) for deciding that a new road is detected when the present location measured by the positioning section is on a road not included in the map information stored in the map information storage section; a new road registration decision section (20) for deciding that the new road is additionally registrable to the map information stored in the map information storage section when the road density in the area including the new road detected by the new road detecting section is equal to or less than a predetermined value; and a new road registration section (21) for making additional registration of the new road, as to which the new road registration decision section makes an additionally registrable decision, to the map information stored in the map information storage section.