The demodulated signal from the optical disk, containing a plurality of addresses is supplied to the address decoder which sets error detection flags when address decoding fails. If all addresses fail to decode, an address interpolator performs address interpolation up to a stored maximum number of iterations, thereby allowing data to be continuously read out from the demodulated signal. The maximum number is stored in memory. If at least one address is decoded, the address interpolator selectively updates the stored maximum number to achieve higher performance in reproducing data items from the optical disk.