An image sensor includes: photoelectric conversion elements configured to receive light and accumulate a charge corresponding to an amount of received light; an imaging signal generating unit that converts the charge accumulated in each photoelectric conversion element into a voltage to generate an imaging signal; and a reference signal generating unit that generates a reference signal having a fluctuation component with a same phase as the imaging signal. The imaging signal generating unit includes: a conversion circuit that converts the charge accumulated in each photoelectric conversion element into the imaging signal; a noise eliminating circuit that eliminates a noise component included in the imaging signal; and an output circuit that outputs the imaging signal from the conversion circuit. The reference signal generating unit includes a circuit having a same structure as that of at least one of the conversion circuit, the noise eliminating circuit, and the output circuit.