1. A vehicle environment monitoring device, which detects bodies present in the environment of a vehicle from infrared images taken by infrared cameras, which comprises: a binarized object extraction device which by binarizing grayscale images of the infrared images, extracts the bodies as binarized objects; a binarized object feature quantity calculation device which calculates a feature quantity of the binarized objects; an object image extraction device which extracts an image of grayscale objects from the grayscale image, the grayscale objects corresponding to the binarized objects; an object image feature quantity calculation device which calculates a feature quantity of the grayscale objects; a feature quantity comparison device which compares to each other the feature quantity extracted by the binarized object feature quantity calculation device and the feature quantity extracted by the object image feature quantity calculation device; and a body state determination device which determines the state of the bodies as affected by a surrounding environment thereof based on the results of the comparison performed in the feature quantity comparison device; wherein said feature quantity comparison device compares for a plurality of bodies the feature quantity extracted by said binarized object feature quantity calculation device and the feature quantity extracted by said object image feature quantity calculation device, and said body state determination device determines the state of said bodies according to a proportion of bodies specified by the results of the comparison of said feature quantity comparison device.