Data recording and/or reproducing method and data recording medium

The present invention is concerned with a method for modulating and recording data, in which the data are modulated in such a manner that m-bit data are converted into n-bit data, where m and n are real integers and m < n, p-bit merging bits are inserted between the n-bit data and the number of consecutive "0"s in the alternate concatenation of these n-bit data and p-bit merging bits is not less than a predetermined number d and not more than a number k which is larger than d, wherein the merging bits of the bit pattern consistent with a digital sum value (DSV) of recording data are inserted between the n-bit data and the DSV is reset at each data block as one unit to facilitate data control for each data block as a unit. The present invention also provides a data recording medium (51) on which are recorded data following this method. When the recording data are demodulated and reproduced from the recording medium (51), it is decided whether the bit pattern of the above merging bit is consistent with the modulation rule and the error detection data which deem the reproduced data in the vicinity of the merging bits not consistent with the modulation rule as being in error are outputted along with the reproduced data to improve the reliability of the reproduced data produced in the reproducing system.