PURPOSE: To perform powerful adaptive equalization by monitoring the impulse response of a line by shifting the center tap of a forward equalizer in a decision feedback equalizer, and performing the switching control of tap correction algorithm corresponding to the above monitoring.

CONSTITUTION: A subtractor 33 takes difference between the output of a c+1 tap multiplier 18 in the forward equalizer 10 and that of a d1 tap multiplier 23 in a backward equalizer 20, and a subtractor 34 outputs the difference between the above difference and a decision signal as an error signal i+1. Tap correction from the center tap c0 to the c+1 tap of the equalizer 10 by LMS algorithm is performed by switching the error signal 1 to the signal i+1 corresponding to the increment of the front edge h1 of the impulse response to main response ho. Also, a tap coefficient control circuit 71 is provided which performs the tap correction by switching the signal to the signal 1 corresponding to the decrement of the front edge h-1 for the main response, and furthermore, changes a tap coefficient by multiplying by a coefficient less than 1 sequentially, and also, returns the tap correction to the one by the LMS algorithm performed by using the signal 1 when the front edge h-l goes to a constant value or zero.