1. An apparatus for reconstructing a panoramic X-ray image, the apparatus comprising: a storage unit for storing image data of multiple image layers; an image processing unit for determining a reference image layer among the multiple image layers, finding blocks that correspond to at least one block designated in the reference image layer from other image layers, selecting a clearest block by comparing image data of the corresponding blocks, and reconstructing the reference image layer by replacing the designated block in the reference image layer with the clearest block selected in any of the other image layers, if the selected block is not the same as the designated block in the reference image layer; and a display unit for displaying a panoramic image of the reconstructed reference image layer.