PURPOSE: To increase a processing speed and to inform a processor of error occurrence in a short time, by executing error detection in a short time after data recording.

CONSTITUTION: A sector recognizing part 11 recognizes whether a specific sector is accessible or not, and the head of the recognized sector is detected by a sector detecting part 21. A data reading part 31 is driven by the output of the detecting part 21 to read data out of a disk 61. This data is inputted to an error detecting part to make an error check, whose result is set to an error reporting part 51 on the completion of the error check. The reporting part 51 reports the error occurrence to the processor 71 after a series of processes.