An analog-to-digital converter includes a first preamplifier receiving a first reference voltage and an input signal, a second preamplifier receiving a second reference voltage and the input signal, a first preamplifier calibrator placed for the first preamplifier and adjusting an input offset of the first preamplifier, a second preamplifier calibrator placed for the second preamplifier and adjusting an input offset of the second preamplifier, an interpolator placed between output terminals of the first and second preamplifiers and generating an interpolation signal having a voltage value between a first output signal from the first preamplifier and a second output signal from the second preamplifier, comparators receiving the first output signal, the second output signal or the interpolation signal and outputting a digital value based on the received signal, and comparator calibrators placed for at least comparators receiving the interpolation signal among the comparators and adjusting input offsets of the corresponding comparators.