To provide a method for detecting faults in an automatic equalizer, that monitors a shift in a center tap factor Cn and identification errors in a control section of the automatic equalizer, so as to detect a fault state which could not be detected using only DC gain and identification errors in an equalizer tap factor, thereby attaining a high-speed convergence of the equalizer.

When the automatic equalizer is diverged due to interruption of a transmission line or the like, the control section 7 of the equalizer monitors the center tap factor Cn of the automatic equalizer and initializes an FF equalizer, when the center tap factor Cn exceeds a range of a threshold tl from a threshold th. Furthermore, in addition to the monitoring of the center tap factor Cn, an error of identification is taken into account, and the step size is made not to change from an initial convergence point until a convergence stable point; while when the identification error is increased from the convergence stable point, the step size is changed stepwise, depending on a change in the identification error to quicken the convergence.