In this instance, by sequentially updating the tap coefficient group with Tc(j+1)=Tc(j)-2???k???Seerr???Sder, tap coefficient group Tc can be controlled so that the square of the absolute value of estimated error signal Seerr may be minimum, where Tc(j) is a value of tap coefficient group Tc at sampling time j??T where the sampling interval is represented by ??T, and k is a parameter which determi