An apparatus for post-processing a reconstructed image is discussed. The apparatus includes an inter prediction unit for generating a prediction block using a reference picture and a motion vector, wherein the prediction block generated by the inter prediction unit is added to a residual block to generate a reconstructed picture; an intra prediction unit for recovering an intra prediction mode for a current prediction unit and generating a prediction block using the intra prediction mode, wherein the prediction block generated by the intra prediction unit is added to a residual block to generate a reconstructed picture; and a post-processing unit for determining a boundary strength for an edge which is a prediction edge or a transform edge on the reconstructed picture, determining whether deblocking filtering is applied on the edge or not using the boundary strength, and filtering the edge in order of vertical edges and horizontal edges if the deblocking filtering is applied on the edge, and for generating an edge index of a current sample, and applying an edge offset corresponding to the edge index to the current sample.