PURPOSE: To realize a good detection characteristic in the case of high-density recording by providing a means which allows such 9-bit word as a code word to correspond to a data word that the number of consecutively appearing '1' is equal to or smaller than a preliminarily determined prescribed integer value.

CONSTITUTION: Nodes S0 to Sn show the internal states or an encoder, and branches indicated by arrows show inter-node transitions, and numbers added to branched show the values of code bits to be outputted. The number of continuously appearing '1's in a word is always equal to or smaller than (n). A state Sn taken in the head of the code word is preliminarily designated by a constant (m) equal to or smaller than (n), and only 9-bit words which end with states S0 to Sn are used as code words with respect to the tail of the code word, and thereby, the number of continuously appearing '1's is always equal to or smaller than (n) even in the case of connection of plural code words. 256 kinds of words corresponding to 8-bit data words are selected from words satisfying these conditions, and they are allowed to correspond to data words.