Abstract: A novel encoding method which facilitates handling at the time of demodulation (decoding) and is capable of further alleviating a burden imposed on a demodulation (decoding) circuit. When an input NRZ code signal is at, for instance, a logical "0" level during a given unit bit time, encoding is effected to obtain a signal having the same form as that of a CMI code such that the signal is set to a logical "1" level in correspondence with a first half of the unit bit time, and to the logical "0" level in correspondence with a second half thereof. Similarly, when the input NRZ code signal is at the logical "1" level during a given unit bit time, encoding is effected to obtain a signal such that the signal is unfailingly set to the logical "1" level during its initial bit time, and thereafter only during a bit time when the NRZ code signal is at the logical "1" level during the unit bit time, the logical "1" level and the logical "0" level are alternately repeated for each unit bit time.