In a charge redistribution type A/D converter, an input-side capacitor terminal and a comparator-side capacitor terminal are connected through first and second analog switches to a fixed-voltage supply circuit, and the input-side capacitor terminal is connected through a third analog switch to the outside. Immediately before sampling an analog signal, the first and second analog switches are closed while the third analog switch is opened, according to a RESET signal. Thereby, fixed voltages are supplied to the input-side capacitor terminal and the comparator-side capacitor terminal, respectively, and charge stored in a weighting capacitor unit is initialized to a predetermined value.