A motion estimating device first detects mobile objects Oi and Oi′ in continuous image frames T and T′, and acquires image areas Ri and Ri′ corresponding to the mobile objects Oi and Oi′. Then, the motion estimating device removes the image areas Ri and Ri′ corresponding to the mobile objects Oi and Oi′ in the image frames T and T′, extracts corresponding point pairs Pj of feature points between the image frames T and T′ from the image areas having removed the image areas Ri and Ri′, and carries out the motion estimation of the autonomous mobile machine between the image frames T and T′ on the basis of the positional relationship of the corresponding point pairs Pj of feature points.