To provide a method for encoding/decoding a PRML code for a high density data storage equipment by enhancing an encoding rate affecting a channel input SNR, improving recording/reproducing of the data, making the encoding rate a specified value and making a maximum continuous transition the specified value.

The input 8 bits data are encoded to a 9 bits code word. The code word satisfying a limit condition of a maximum transition length MTR = 3 is generated. A signal recorded on a storage equipment is immunized against a main cause carrying a noise and a signal distortion through compression by a compression encoder 10 and encoding by an error correction encoder 20. Then, the signal is encoded by an RLL modulation encoder 30 adapted to the channel characteristic of the storage equipment, and the signal is generated by a signal generator 40, and is recorded/reproduced after the signal is beforehand compensated by a write-in equalizer 50, and is processed by a read-out equalizer 60, and the signal is detected so as to minimize error probability through a detector 70.