To make it possible to make the enhancement of the high speed following properties to the amplitude fluctuation of a reproduction signal and the securement of the stability to a medium defect or the like compatible with each other, when a mark position recorded recording medium is reproduced.

In the differential signal obtained by differentiating the reproduction signal, after the peak exceeding a prescribed level of the differential signal is detected, if the peak is detected to be changed to a peak having reverse polarity and exceeding a prescribed level in a fixed period, the zero-cross detection signal between the peaks is adopted as a mark detecting signal, in the mark detection when the mark position recorded recording medium is reproduced.