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 q₀q₁ 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. For example, code states s₀ and s₁ when information sequences d₀ and d₁ 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, s₀=s₁=6, in a third block, and two's complement q₀ of a sum of code sequences c₀ up to a time when the code states are equal to each other is "0" while two's complement q₁ of a sum of code sequences c₁ up to that time is "1". That is, the condition that q₀q₁ is met. The present invention can be applied to a recorder/player or encoder.