PURPOSE: To improve an efficiency to correct errors in a simple constitution and reduce a redundancy while maintaining convertibility with a CD, by improving a code length, a constitution of a frame sector and the like.

CONSTITUTION: When a digital signal is to be coded, a code length is set to be a length of several frames and the number of convection parities (R1, R2) for correction of errors is increased and coded in comparison with a standard of a compact disc. One sector is made equal to the actual number of data in one sector of the compact disc standard, and a frame length is set approximately equal to a frame length of the compact disc standard. A sub code of one byte is added successively to a frame synchronous signal at the head of a frame. Accordingly, a redundancy is reduced as compared with the compact disc standard, a recordable quantity of data is increased and convertibility with the CD is maintained.