PURPOSE: To adaptively update a filter characteristic through a small amount of arithmetic operation, and in addition, to reduce power consumption by providing a tap gain updating part and a memory part to store many filter characteristics.

CONSTITUTION: In order to optimize the filter characteristic of an adaptive equalizer, an error estimating part 3 estimates an error e(t) on the basis of the output a(t) of a training reference signal generating part 6 by the output x(t) of a transversal filter part 1 and the estimated value a(t) of this output estimated by a data discriminating part 2 or the switching operation of a switching part 5. The tap gain updating part 4 reads a parameter to determine the filter characteristic to minimize the error e(t) out of the memory part 7, and outputs it as the coefficient of each coefficient multiplier 1b of the filter part 1. Through this configuration, the filter characteristic can be updated adaptively, and waveform can be equalized. Besides, since the arithmetic operation required for updating the coefficient of each coefficient multiplier 1b of the filter part 1 is reduced, the power consumption can be curtailed.