Abstract: A coefficient update circuit, an adaptive equalizer including the coefficient update circuit, and a coefficient update method of the adaptive equalizer are provided. The coefficient circuit includes: an error level detector, which detects the level of an error signal that is a difference between the level of an output signal of the adaptive equalizer and a desired signal level; and a plurality of coefficient generators, which generate current filter coefficient values by adding update values designated by the level of the error signal and the levels of delayed input signals to previous filter coefficient values, the delayed input signals being generated by delaying an input signal of the adaptive equalizer for a predetermined amount of time. The generated current filter coefficient values are provided to a filter included in the adaptive equalizer.