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 a 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 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 based on the results of the comparison performed in the feature quantity comparison device.