To attain the highly accurate reproduction of the recorded multi-valued information stream when this multi-valued information stream is recorded with high density on a recording medium such as an optical disk.

The correction information of the multi-valued information stream formed by arranging values from 1 to n-1 (n is integer ≥3) recorded on the optical disk 1 and adding a plurality of 0s before and after each value, and the user information of the multi-valued information stream are reproduced, then the maximum value of reproduced signals of each value from 1 to n-1 of the reproduced correction information is obtained by a demodulating circuit 8, and the waveform equalizing process is decided, which makes each amplitude out of the range separated by the multi-valued data period of each value before and after the respective maximum values to be almost 0 with respect to each reproduced signal, and the waveform equalizing process based on the above decided waveform equalizing process is applied on the reproduction signal of the reproduced user information.