The invention provides an encoding device, a decoding device, an encoding method and a decoding method which enhance optimality in a situation of encoding moving image signals having no sample ratio distinction between color components such as a 4:4:4 format. In a situation of conducting compression encoding by inputting digital moving image signals of the 4:4:4 format, 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 are prepared. The encoding process is executed by selecting any one of the first encoding process and the second encoding process, and makes the compression data comprising an identification signal for indicating which process is selected.