An analog-to-digital converter includes an input terminal, a first comparator, a first output terminal, a second comparator, and a second output terminal. The first comparator generates a first logical signal and a control signal by comparing an input signal received by the input terminal with a first reference signal. A first transistor generates a first current based on the input signal. First and second switches are switched so as to be short-circuited/open-circuited in an opposite manner to each other based on the control signal. A second transistor supplies a second current based on a second reference signal to a terminal when the first switch is ON. A third transistor supplies a third current based on a third reference signal to the terminal when the second switch is ON. An output unit generates a second logical signal by comparing the first current with one of the second and the third currents.