1. An apparatus for acquiring an internal-structure image of an object from a plurality of images of the object, the apparatus comprising: a photographing unit to photograph the object by capturing light reflected from the object, the light radiated from at least one of a plurality of light sources; a control unit to control the photographing unit and the at least one light source to obtain a first image and a second image under different photographing conditions in which angles formed by the at least one light source, convexity/concavity on surface of the object, and the photographing unit are different; and an extracting unit to extract a third image that is common to the first image and the second image, the third image corresponding to the internal-structure image.