The object of the present invention is to realize reduction of the level
jitter generated from a noise component at a signal saturation level or a
waveform distortion in a portion except for signal polarity portions
(rising edge and falling edge), and good error characteristics. In the
present invention, a predetermined upper or lower limit value is set to
reproduction signals, the reproduction signals are subjected to a limiter
processing for correcting reproduction signals of the upper limit value
or more, or the lower limit value or less to the level of the upper limit
value or the lower limit value, respectively, the signal subjected to the
limiter processing is subjected to a partial response equalizing (PR
equalizing) processing, and PR reproduction is performed to improve the
level jitter at PR detection time and the error rate at information
reproduction time.