An error pulse is generated from a PRML circuit, and reproduction compatibility with a conventional apparatus is established. After a reproducing signal output from an optical head is equalized by an analog equalizer, sampled by an A/D converter at every clock, and digitally equalized by a FIR filter, the signal is binarized by a PRNL decoder. On the other hand, with regard to an error pulse, a level at an edge point is detected from an output signal of the A/D converter by an edge level detector, and the level at the edge point and an error pulse detection threshold are compared by an error pulse generator, and the error pulse is generated. Even when an optical apparatus having a trial writing function using conventional error pulse is provided with a PRML reproducing system for enablinghigh speed, the optical apparatus can execute trial writing using the error pulse as it is.