To suppress the deterioration of the inertial calculation precision increased as time elapses and improve the guidance precision to a target in a navigation device for a flying object.

This navigation device is provided with an inertial device 11 outputting the position, speed and attitude angle of a flying object, an image pickup device 13 fitted to the front of the flying object and obtaining a front pickup image, and a means 12 calculating the self-attitude angle from the image photographed by the image pickup device 13. The attitude angle obtained from the image is compared with the attitude angle calculated by the inertial device 11, and the attitude angle error of the inertial device 11 is estimated and corrected based on the difference.