1. A motion estimating device that captures images of an ambient environment of an autonomous mobile machine by using an imaging device, and estimates a motion state of the autonomous mobile machine on the basis of a change in 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 a positional relationship between the corresponding feature points of the respective captured images.