Provided is an equalizer including: an input amplifier configured to amplify and output an input signal; a first equalization circuit including a first sampling circuit, a first arithmetic circuit, and a second arithmetic circuit, the first sampling circuit being configured to generate and output 1-1 to 1-N feedback signals, wherein N is a natural number greater than or equal to 2; and a second equalization circuit including a second sampling circuit, a third arithmetic circuit, and a fourth arithmetic circuit, the second sampling circuit being configured to generate and output 2-1 to 2-M feedback signals, wherein M is a natural number greater than or equal to 2.