A background lighting module illuminates an object from behind by visible light with respect to a photographing module to identify an area including the boundary between the object and the background portion in an image to be photographed by the photographing module. A controller controls a photographing operation including the exposure of the photographing module and the lighting intensity of the background lighting module. An image processing module processes the images photographed by the photographing module. The controller sets the exposure and lighting intensity to specific conditions so as to photograph a processing image where the background portion on the periphery of the object has a higher luminance than that of the silhouette portion of the object. The image processing module extracts the shape of the object by using the luminance difference between the silhouette area of the object and the background area on the periphery of the object.