A modulator that quantizes a first signal into a quantized signal having a plurality of bits includes an integrator performing sampling on the first signal in a first period, and to integrate a difference between the first signal and a reference signal in a second period; and a quantizer receiving a second signal which is an output of the integrator and operating in synchronization with a first clock having a cycle shorter than the first period, the quantizer generating the quantized signal on the basis of the second signal in the first period and outputting the reference signal on the basis of the quantized signal to the integrator.