1. A method of reconstructing a skeletal image, the method comprising: determining a region of interest (ROI) to be processed at a high resolution with respect to a skeletal image captured from an inspection target; and reconstructing a high-resolution skeletal image by performing a finite element method (FEM) and topology optimization on the ROI, wherein the reconstruction of the skeletal image comprises: performing meshing on the skeletal image comprising the ROI; converting a bone mineral density (BMD) or BMD-related value of bone corresponding to the meshed ROI to an elastic modulus; applying the elastic modulus to each finite element constituting the ROI; applying a predetermined load condition to a finite element model to which the elastic modulus is applied; calculating a strain energy of each finite element based on the displacement of a finite element model to which the load condition is applied; and determining a density value of each finite element based on the strain energy of each finite element.