A voltage detector that detects an AC voltage in an object includes: an electrode disposed facing the object; a current-to-voltage converter that has a first input set at a reference voltage and a second input connected to the electrode and converts a detection current, which corresponds to a potential difference between the detected AC voltage and the reference voltage on a path including the electrode and a feedback circuit connected to the second input, to a detection signal; an integrating circuit that integrates the detection signal and outputs an integrated signal whose amplitude changes in accordance with the potential difference; an insulating circuit that inputs the detection signal or the integrated signal, and outputs the signal so as to be electrically insulated from the input; and a voltage generating circuit that generates the reference voltage by amplifying a signal based on the integrated signal to reduce the potential difference.