There are provided an encoding device, a decoding device, an encoding method, and a decoding method that enhance optimality in a case of encoding moving image signals having no sample ratio distinction between color components such as a 4:4:4 format. In a case of conducting compression encoding by inputting digital moving image signals of the 4:4:4 format, there are prepared a first encoding process of encoding three color component signals of the input moving image signals in a common encoding mode, and a second encoding process of encoding the three color component signals of the input moving image signals in respective independent encoding modes. The encoding process is executed by selecting any one of the first encoding process and the second encoding process, and the compression data contains an identification signal for specifying which process is selected.