To realize a digital equalizer filter with few multipliers by using knowledge before the regulated edge point value of a transmission function by means of a plurality of multipliers.

An input signal xn-2 which is delayed by a two hours unit by unit delays 104 and 106 from an input signal xn is subtracted by an addition element 108 and a multiplier 112 executes multiplication by the result. An addition element 114 adds an input signal xn-2 which is delayed by two hours unit to the product of the multiplier 112. An output signal yn-1 delayed by a one hour unit by unit delay 116 is subtracted from an input signal xn-1 which is delayed by unit delay 104 by the one hour unit in an addition element 118 and a multiplier 122 executes multiplication by the result. An addition element 124 adds the product of a multiplier 122 to the result of he addition element 114 and an output signal yn-2 delayed by the two hours unit by unit delays 116 and 126 is subtracted from the input signal xn-2 delayed by the two hours unit in an addition element 128. An addition element 132 executes multiplication by the result and a product is added to the result of an addition element 134.