A map information processing apparatus includes an intersecting determining means (20) for determining intersection points where a new road detected by a new road detecting means (19) intersects either roads included in map information or roads previously detected by a new road detecting means, other than start and end points of the new road, a road update information generating means (21) for generating road update information including information for updating new road information and road information included in the map information based on new road information about the detected new road and intersection information indicating the intersection points determined by the intersecting determining means, and a road information updating means (24) for updating the road information included in the map information based on the road update information, and for writing the new road information into a new road information storage means (16b).