1. An apparatus for restoring a cubical object, comprising: a vanishing point computing part configured to compute vanishing points corresponding to an image; an image depth computing part configured to compute an image depth of a cubical object in the image; a central rectangle computing part configured to compute a central rectangle based on a representative rectangle of the image and the vanishing points; a restored rectangle computing part configured to compute a restored rectangle corresponding to the central rectangle and a projection center point using a coupled line camera (CLC) method; a cube depth computing part configured to compute a restored cubical object depth based on the central rectangle, the restored rectangle and the projection center point; and a cube restoring part configured to restore the cubical object to the image to thereby form a restored cubical object in the image, the restored cubical object having the restored rectangle as one surface thereof and having a depth of the restored cubical object depth, wherein the cube depth computing part is configured for: disintegrating the image depth into two diagonal vectors of the central rectangle; converting the two diagonal vectors into two diagonal vectors of the restored rectangle; computing a depth of the restored rectangle by adding the two diagonal vectors of the restored rectangle with each other; and computing a restored cubical object depth based on the depth of the restored rectangle and the projection center point.