The tracks in a read-only area are divided into sector regions having the same capacity, error correcting codes are added to 1st data signals to generate 2nd data signals and pit rows are formed in the sector regions to record data. In a rewritable area, recorded user data are correlated with 1st data, the same error correction codes used for the read-only area are added to the 1st data signals to generate 2nd data signals in a similar way and data signals for making rewritable are added to the 2nd data signals to generate 3rd data signals. A format is set up by adding a header region where sector address information is recorded to a region in which the 3rd data signals are recorded. The region is divided into two areas radially, the outer area being made a rewritable area and the inner area being made a read-only area. Control data signals are recorded in the read-only area.