A navigation device comprises a signal processing unit (12)for measuring the pseudo distance/rate of change of the pseudo distance of a GPS satellite which is an emission source of a radio wave received by a radio wave receiving unit (11) and obtaining a navigation message from the radio wave, a GPS satellite behavior estimating unit (13) for calculating the CPS satellite position/speed from the navigation message, a pseudo-distance error estimating unit (14) for estimating the pseudo-distance error from the pseudo distance and rate of change of the pseudo distance, a user position observing unit (15) for calculating the position of the navigation device from the pseudo distance, GPS satellite position, and pseudo-distance error, a user speed/direction observing unit (16) for calculating the speed of the navigation device from the rate of change of the pseudo distance, GPS satellite position, and the position of the navigation device, and a user direction searching unit (17) for searching for, as the direction of the navigation device, the direction in which when the multipath error in the pseudo-distance error is less than a predetermined value, the rate of change of the pseudo distance calculated from the relative movement between the navigation device and the GPS satellite when the direction is changed within a predetermined angle range matches the measured rate of change of the pseudo distance.