There is disclosed a modulation method in which a four bits unit of a plurality of continuous input data words is encoded into a six bits unit of a plurality of continuous output code words by referring to a plurality of coding tables (13) including output code words (C(k)) corresponding to input data words (D(k)), and coding table designation information (S(k+1)) in which an coding table for use in encoding the next input data word is designated. Further, in particular, two redundant bits are inserted into each predetermined number of data words of the plurality of continuous output code words. Even with such redundant bits, a DSV control is possible, k satisfies 9 in a (1, k) RLL rule, and a repetition frequency of a minimum run is limited.