To provide an updating block which can process complex number coefficients without increasing the hardware so much mainly in the adaptive equalizer filter array of a RAM base.

For a complex number, a coefficient updating expressions become COr(n+1)=COr(n)+er(n-a)Xr(n-i-a)-ei(n-a)Xi (n-i-a) and COi(n+1)=COi(n)+ei(n-a)Xr(n-i-a)+er(n-a) Xi(n-i-a), where the CO, X, and (e) respectively represent the coefficient, input signal sample, and error signal sample and the (a), (r), and (i) respectively represent an additional delay, real part, and imaginary part. For processing the Xr(n-i-a) and Xi(n-i-a), an updating signal, unit 710 is used. The sum Xsum of the real part Xr and imaginary part Xi of the X and the difference Xdif between the parts Xr and Xi and the real part er and imaginary part ei of the error signal sample are supplied to the unit 710. When a code LMS, namely, er and ei are fixed to ±1 only, the above-mentioned equations become addition and subtraction of the Xsum and Xdif to and from the CO. Therefore, an adder/subtracter 720 is used for the addition and subtraction of coefficients supplied from the loops 725-740 of a delay unit.