An analog/digital converter apparatus includes a reference signal generator circuit for generating a reference signal, a comparator section for determining a relationship in level between an input analog signal and the reference signal, and an encoder for converting a comparison result of the comparator section into a digital signal as an output signal. The comparator section has a comparator for comparing the input analog signal with the reference signal and a switching circuit which is interposed between the comparator and each of an input terminal for the input analog signal and a reference signal output terminal for the reference signal and used for switching the input signal lines of the comparator to compensate an equivalent input offset.