1. A face region estimating device for estimating a person's face region contained in a plurality of picked-up images from the picked-up images taken of a mobile body by a plurality of cameras, comprising; a distance information generating unit for generating a distance to the mobile body as distance information, based on an azimuth difference of the plurality of picked-up images; a motion information generating unit for generating motion of the mobile body as motion information, based on a difference of the picked-up images inputted in time series from at least one of the plurality of cameras; an object distance setting unit for setting an object distance in which the mobile body exists, based on the distance information and the motion information; an object distance image generating unit for generating an object distance image composed of pixels corresponding to the object distance, based on the distance information; an object region setting unit for setting an object region containing the region of the mobile body, corresponding to at least the object distance set by the object distance setting unit in the object distance image; an outline extracting unit for extracting an outline from the object region set by the object region setting unit; a head region setting unit for setting a head region assuming the mobile body to be a person, based on a pixel distribution of the object distance image corresponding to a predetermined range on the basis of a pixel position at the upper part of the outline extracted by the outline extracting unit; and a face region extracting unit for extracting the person's face region from the picked-up image, based on the color distribution of the picked-up image corresponding to the head region set by the head region setting unit.