To provide an adaptive equalizer which has a configuration suppressing the increase of a circuit scale due to multipliers etc, and requires small power consumption, and comprises many filter taps.

An approximation unit 30 approximates the value of a received digital signal to a predetermined value. The predetermined value is a bit shift number. A filter unit 32 executes equalizing processing based on a filter tap for inputting an approximated signal. A determination unit 36 compares the signal outputted from the filter unit 32 with a threshold prepared beforehand, and determines the transmitted information signal according to the result of the comparison. An adder unit 38 conducts subtraction processing in order to obtain an error signal 84 between the outputted signal from the filter unit 32 and a signal determined at the determination unit 36. A coefficient computation unit 34 conducts signal processing based on the error signal 84 to calculate the filter tap coefficient for the filter unit 32.