PURPOSE: To enhance error correction ability in an optical disk by detecting an error condition at every zone of the zone divided optical disk, fixing the number of blocks in a format divided into respective optical heads of an optical head pair at every zone and varying a data amount and an error correction code amount added to the data with the optical head pair.

CONSTITUTION: The data of a signal generation circuit 13 are recorded on the optical disk 7, and the reproduced data are compared by a verify circuit 15, and an error characteristic at every zone is detected. Then, by the judgement of a micro computer 16, the data amount in the block of the format divided to respective optical head pairs and the error correction code amount added to the data are varied so as to match the format at every zone in a format forming circuit 2 and an error correction code generation circuit 3. Thus, the error correction matching the error characteristic of respective zones on the optical disk are obtained.