The own vehicle position estimator 17 of the in-vehicle device 1 acquires the predicted own vehicle position X− (t) that is a predicted value of the present position and the orientation of the moving body. Then, the own vehicle position estimator 17 acquires: the relative angle Lψ (t) that is first orientation information indicative of the orientation of the landmark with respect to the vehicle specified based on the measurement data of the landmark by the lidar 2; and the relative angle L−ψ (t) that is second orientation information indicative of the orientation of the landmark with respect to the vehicle into which the orientation of the landmark indicated by the landmark information is converted. The own vehicle position estimator 17 corrects the predicted own vehicle position X−(t) based on the difference between the relative angle Lψ(t) and the relative angle L−ψ(t).