A ΔΣ analog-to-digital converter includes a previous stage amplifier circuit which amplifies an input signal, a conversion circuit which converts an analog signal into a digital signal, where the analog signal is output from the previous stage amplifier circuit, an input node provided in the previous stage amplifier circuit, a plurality of capacitors provided in the conversion circuit, a first amplifier and a second amplifier, and a path switching circuit which connects the first amplifier to the input node in a first mode and connects the first amplifier to the plurality of capacitors in a second mode, where the first mode is for sampling the analog signal and the second mode is for performing an integration operation. The first amplifier forms the previous stage amplifier circuit in the first mode, and forms an integrator which carries out the integration operation performed in the conversion circuit in the second mode.