1. A data encoding device, comprising: an encoding table for correlating a data element with a code word such that one data element is correlated with N number of code words and one code word is correlated with one data element, the data element serving as a unit of data encoding, N being an integer larger than zero; a retrieve unit for determining a data element corresponding to each of a series of encoding data and for retrieving the N number of code words correlated with the determined data element with reference to the encoding table; a selector for selecting one code word from among the N number of code words according to predetermined criteria; and a generator means for generating, as required, additional information which specifies encoding data correlated with the selected code word among one or more encoding data corresponding to the determined data element correlated with the selected code word, whereby each encoding data is converted into either additional information attached encoded data or normal encoded data, the additional information attached encoded data consisting of a code word and additional information, the normal encoded data consisting of a code word.