An adaptive equalization circuit (105) operates for PR-equalization of the reproduced signal that is subjected to an A/D conversion by an A/D converter (103) and shaped by a waveform shaping circuit (104). An ideal-waveform generation circuit (110) generates an ideal waveform that corresponds to the reproduced signal that is binarized by a Viterbi-decoding circuit (108). A mark-length/space-length calculation circuit (112) calculates the actual mark length/space length relative to the mark length/space length to be formed, based on the equalization error that arises when the ideal waveform assumes a central reference level as calculated by an equalization-error calculation circuit (111) and the intervals of polarity inversions of binarized data detected by a 0-cross detection circuit (109). A system controller (114) adjusts the edge shift quantity of the recording waveform when forming a mark based on the calculated mark length/space length.