An optical disk playback apparatus for playing back or reproducing main data and its associated sub-code which are read from an optical recording medium comprises an interleave RAM for storing the main data. The optical disk playback apparatus performs a predefined synchronization protection on synchronization information included in the sub-code to generate a sub-code synchronization signal which is written into an empty area of the interleave RAM, and manages the addresses with a FIFO area in a manner similar to the main data, thereby causing the read sub-code synchronization signal to function in synchronization with the main data.