In a comparator of an analog-to-digital converter, an input signal is input to a control terminal of each of a plurality of signal input transistors. A signal input transistor selection section selects any one of the plurality of signal input transistors, and generates a current in response to a difference between the input signal and a reference signal to flow in the differential pair configured with the selected signal input transistor and a reference input transistor. A load section converts, at a time of a change of a current flowing in any one of the plurality of signal input transistors and the reference input transistor in response to the difference, the change of the current into a change of a voltage, and outputs the change of the voltage as a result of comparison between the input signal and the reference signal.