In an A / D converter circuit having a chopper comparator, only a small number of elements are additionally provided to impart a hysteresis characteristic to the comparator, thereby reducing the conversion errors caused by noise. In a successive approximation type A / D converter circuit having a chopper comparator, one or more amplifier stages are provided to the comparator circuit (CMP), and a feedback capacitor (Cf), which is connected to the input terminal of one of the amplifier stages, is also provided to the comparator circuit (CMP). In the A / D converter circuit, during a first interval, an input analog voltage is taken in, and during a second interval, a voltage, which is in accordance with a potential difference between the input analog voltage and the comparison voltage, is inputted and the input potential is amplified by the amplifier stages. When the output of the comparator circuit changes, a positive feedback is applied through the feedback capacitor to the input terminal of the corresponding amplifier stage, thereby providing a hysteresis of 1 LSB or less.