1. A motion estimating device that captures images of an ambient environment of an autonomous mobile machine by using an imaging device, and estimates the motion state of the autonomous mobile machine on the basis of a change in the respective captured images of the ambient environment, the motion estimating device comprising: an image area removing section detecting mobile objects which exist in the respective captured images of the ambient environment, and removing image areas corresponding to the mobile objects; a corresponding feature point extracting section extracting corresponding feature points from the respective captured images having removed the image areas corresponding to the mobile objects; and a first estimating section estimating the motion state of the autonomous mobile machine on the basis of the positional relationship between the corresponding feature points of the respective captured images.