To improve performance for suppressing the waveform interference of a signal stream in the state of maintaining the stability of an AGC loop by comparing a level fluctuation value in the signal cycle of the signal sequence with a reference value, averaging the signal level fluctuation of the signal sequence through the adjustment on the preceding step side of an equalizer based on this result and controlling the reference value based on the signal level fluctuation value of an output signal from the equalizer.

In a signal processing circuit 2 of a digital signal recording and reproducing device, a gain is corrected by a first signal level control loop composed of a signal adjuster 21, first low-pass filter(LPF) 41, comparator 45 and third LPF 47 provided on the preceding step side rather than an equalizer 13 to generate signal delay concerning a signal level fluctuation component having jitter fluctuation in the repetition cycle equal with or faster than a frequency having the same repetition cycle as the basic cycle of a regenerative signal {yk} in the fluctuation component of the regenerative signal {yk}. Thus, even when quick-response gain correction is performed, this gain correction is not made unstable.