1. An encoding method perform by an encoding apparatus, comprising the steps of: reading, by the encoding apparatus, block data, one by one, from an original image; defining a position of the block data; extracting lower bit-plane data from the block data; extracting upper bit-plane data, which is obtained by subtracting the lower bit-plane data from the block data, form the block data; providing a generator polynomial; generating redundant code data based on the upper bit-plane data, using the generator polynomial; forming encoded lower bit-plane data, in which the redundant code data is embedded; and creating encoded block data, in which the encoded lower bit-plane data and the upper bit-plane data are combined.