A composite read-only and rewritable type optical disc, and a disc drive apparatus for reading/writing data into the disc. The optical disc has a plurality of sectors forming a data read-only area and a write/read area. The disc includes a recording film formed over its entire surface by which data can be recorded on the disc. Each area has track sectors each having a sector identifier portion in which address information is recorded and a data field portion to record data. Data-field identification flags indicative of the read-only area and the write/read area are recorded in the respective identifier portions. On reading or writing this optical disc, the data field identification flag is detected to identify the kind of related area, i.e., whether it is a read-only area or a write/read area. Thus, it is possible to avoid erroneous recording of data into the read-only area. Upon executing a reading operation, waveform equalization and binary-clipping level of reproduction signals can be well controlled. The gain of the servo loop can be switched. The track searching operation can be stably performed. The reading and writing of data with respect to the data write/read area can be improved.