PURPOSE: To correct an estimate position and an estimate azimuth to be on an adjacent road with a small azimuth difference by generating a virtual road among object roads when plural object roads exist to correct the estimated position and azimuth.

CONSTITUTION: When two roads 331, 332 whose azimuth difference from an estimated azimuth 323 calculated by an estimate position estimate azimuth arithmetic means 131 and whose distance from an estimate position 313 are a prescribed value or below exist adjacently to each other, an object road calculation means 132 takes a reciprocal of an area 333 between the roads 331 and 332 as a correlation value and generates a virtual road 341 by which the area 333 surrounded by the roads 331 and 332 is divided equally. Then a position azimuth correction means 134 corrects the estimate position 313 and the estimate azimuth 323 to a position 342 and an azimuth 343 on the virtual road 341. Thus, when roads with a very small azimuth difference exist adjacently, an event of the position of a vehicle not identified is avoided.