PURPOSE: To halve number of multipliers with respect to a tap number by employing a same type of multiplier for an i-th tap multiplier and an (m-i+1)th tap multiplier.

CONSTITUTION: The filter consists of (m-1)/2 sets of adders 21 summing signals of i-th tap (i=1,2,..., (m-1)/2) (m is an odd number) and a signal of (m-i+1)th tap, (m-1)/2 sets of multipliers 13 receiving outputs of the adders and multiplying a prescribed tap number with the signals, a multiplier 13 receiving a signal of an (m+1)/2 tap and multiplying a prescribed tap coefficient with the signal and an adder 15 summing outputs of each multiplier. Thus, a same multiplier is used for the i-th tap multiplier 13 and the (m-i+1)th tap multiplier. Thus, number of the multipliers in use is halved with respect to the tap number.