To shorten an arithmetic processing time in a conventional adaptive filter by performing a convolution arithmetic operation and a norm arithmetic operation in the same arithmetic loop.

A reference signal Xj is inputted to the delay line of an adaptive filter, and a convolution arithmetic operation is executed, and the sum of squares of the reference signal is successively calculated. Then, those arithmetic operations are executed the same number of times as the number of taps, and when it is judged as Yes, a difference between a control signal Zi and a convolution output Yj is calculated so that an error signal Ej can be obtained. Then, a coefficient updating arithmetic operation is performed in an S6. When this coefficient updating arithmetic operation is executed the same number of times as the number of taps in the arithmetic loop, a series of processing is ended. Then, the above mentioned arithmetic operation is repeated.