A code sequence is encoded using a code conversion table in which the parity of the code sequence varies until the code states become equal to each other. The code word assignment used in this code conversion table is such that the decoded code word constraint length is 3 blocks and q.sub.0.noteq.q.sub.1 for an arbitrary information sequence is satisfied even if a DC control bit is inserted at any of the first and second bits of an information word. Code states s.sub.0 and s.sub.1 when information sequences d.sub.0 and d.sub.1 resulted from insertion of provisional DC control bits 1 and 0 inserted at the top of an information sequence "1, 1, 0, 0, 0, 1, 0" are encoded starting with a state 3 according to a predetermined code conversion table are equal to each other, namely, s.sub.0=s.sub.1=6, in a third block, and two's complement q.sub.0 of a sum of code sequences c.sub.0 up to a time when the code states are equal to each other is "0," while two's complement q.sub.1 of a sum of code sequences c.sub.1 up to that time is "1". That is, the condition that q.sub.0.noteq.q.sub.1 is met. The code sequence can be applied to a recorder/player or encoder.