To restrict the number of continuing times of minimum run while performing efficient DSV control by keeping the minimum run and maximum run by the RLL code of minimum run d=4.

Modulator 1 converts a variable length code sequence (d, k; m, n; r)=(4, 21; 2, 5; 6) to a data stream according to a first inversion table. A VFM-PP modulation part 12 modulates a data stream to which a DSV control bit is inserted by a DSV control bit decision and insertion part 11 according to the first inversion table to generate a data stream and outputs it to a NRZI part 13 for making NRZI (Non return to Zero inversion). The conversion code of the first inversion table is the minimum run d=4 and the maximum run k=21, and a conversion ratio has variable length structure of m/n=2/5. In the first inversion table, an exceptional conversion rule is provided for keeping the minimum run d=4, and a plurality of update codes are provided by different constraint length for restricting the continuity of the minimum run d in addition.