An analog-to-digital converter includes a digital-to-analog (DA) converting part having a predetermined number of gradation converting stages and configured to cause each of the predetermined number of gradation converting stages to convert a digital signal to an analog signal and output the converted analog signal, a main-comparator configured to output a binary signal on the basis of a first comparison result between the analog signal output from the DA converting part and a predetermined reference level, and a second sub-comparator having an offset less than a quantization unit with respect to the main-comparator and being configured to output a binary signal on the basis of a second comparison result between the analog signal output from the DA converting part and the predetermined reference level.