Provided is a re-encoding method including obtaining a first quantization table from a bitstream including an image encoded using the first quantization table; obtaining a second quantization table based on a pattern representing a size distribution of values of elements of the first quantization table, the second quantization table including elements respectively corresponding to the elements of the first quantization table; and re-encoding a reconstructed image by using the second quantization table, the reconstructed image being obtained by decoding the encoded image by using the first quantization table.