An A/D conversion apparatus includes a signal processor, a quantizer, and a controller. The signal processor has circuit blocks connected in a loop to process an analog input signal. The quantizer generates a quantization value by quantizing an output of at least one of the circuit blocks including a final-stage circuit block. In each circuit block, one end of a first capacitor is connected through a switch to an input terminal of an operational amplifier, and one end of each of second and third capacitors is connected directly to the operational amplifier. The controller generates an A/D conversion result of the analog input signal according to the quantization value and changes connection conditions of the capacitors so that the signal processor and the quantizer function as a delta-sigma modulator or a cyclic A/D converter.