A modulator includes an integrator, an input chopping switch, and output chopping switch, and a control circuit. The integrator has a differential amplifier, a first switch and a series circuit. The first switch is connected between input and output terminals of the differential amplifier. The series circuit is connected between the input and output terminals of the differential amplifier. The series circuit has a second switch, an input capacitance chopping switch, an integration capacitor and an output capacitance chopping switch. The control circuit controls the input chopping switch and the output chopping switch to execute chopping being at a chopping frequency identical to the input capacitance chopping switch and the output capacitance chopping switch. The chopping frequency of the input and output capacitance chopping switches is lower than a switching frequency of the first switch.