A method for decoding data stored in a disk is achieved by demodulating a physical cluster read out from the disk and outputting LDC (long distance code) data and BIS (burst indicator subcode) data included in the physical cluster, temporarily storing part of the LDC data and BIS data of the data included in the physical cluster in a first memory portion, reading out the LDC data and BIS data stored in the first memory portion and storing the read out data in a second memory portion, reading out LDC data and BIS data requiring error correction from the second memory portion and temporarily storing the read out data in the first memory portion, and storing LDC data and BIS data for which data processing operation including the error correction operation is completed in the second memory portion.