Navigation device and navigation method

A navigation device comprises a unit that acquires an estimated position of a vehicle based on dead reckoning navigation, a unit that acquires a GPS position of the vehicle based on GPS, a unit that sets the candidate points for the vehicle position on roads in the vicinity of the estimated position, a unit that calculates for each candidate point a normal cost of the candidate point with respect to the estimated position, a unit that calculates for each candidate point a correction cost that corresponds to a value found by subtracting a width of a road set with a candidate point from a distance between the GPS position and the candidate point, and a leading candidate point identification unit that identifies the leading candidate point based on a total cost of the normal cost and the correction cost for each candidate point.