A circuit device includes a register that stores result data, a D/A converter that executes D/A conversion on the result data so as to output a D/A conversion voltage, a comparator that compares an input voltage with the D/A conversion voltage, and a processing circuit that executes an update process on the result data through a determination process based on a comparison result from the comparison portion, so as to obtain A/D conversion result data of the input voltage, in which the processing circuit executes the determination process on an MSB side of the A/D conversion result data in a first determination period, and executes the determination process on an LSB side of the A/D conversion result data in a second determination period longer than the first determination period.