To realize a scrambling of high reliability and small in circuit scale, without the occurrence of a correlation dependent upon recording position by using a plurality of selectable M sequences.

Each of output bits which are successively bit-shifted in the shift direction in individual stages R0 to R13 of a 14-stage shift register 101 selects an M sequence, which is generated by a prescribed primitive polynomial corresponding to a scramble number based on position information of a disk, from a selection table in a feedback bit selector 102. Then, three selection bits s1, s2, and s3 according to the connection relation of the selected M sequence are outputted, and exclusive ORs between them are operated in order by EXOR circuits 103a to 103c, and they are fed back to the first stage R0. The M sequence generated in this manner is used to scramble recording data, and thus scrambling of less correlation and high reliability is realized independently of the recording position.