A variable reference voltage source that generates a variable reference voltage corresponding to setting data set from outside includes a control unit including a calibration control unit that controls operation for acquiring calibration data including calibration values of an offset voltage and a predetermined unit voltage of a determiner, which determines magnitudes of two voltages, and an output control unit that controls operation for generating, based on the calibration data, a variable reference voltage corresponding to the setting data set from the outside, a reference voltage unit that outputs a reference voltage, and an integrated-voltage generating unit that repeats, when the calibration control unit controls the operation, an integrating operation until an integrated voltage obtained by integrating at least two or more kinds of unit voltages becomes equal to the reference voltage and outputs, when the output control unit controls the operation, the variable reference voltage corresponding to the setting data.