1. A shape extraction apparatus comprising: a photographing module which photographs an object; a background lighting module which illuminates said object by visible light from behind with respect to said photographing module to identify an area including the boundary between said object and the background portion in an image to be photographed by said photographing module; a control module which controls a photographing operation including the exposure of said photographing module and the lighting intensity of said background lighting module; and an image processing module which processes the image photographed by said photographing module, wherein said control module sets said exposure and lighting intensity to specific conditions so as to photograph a processing image where the background portion on the periphery of said object has a higher luminance than that of the silhouette portion of said object, and said image processing module extracts the shape of said object by using the luminance difference between the silhouette area of said object and the background area on the periphery of said object in said processing image.