A voltage sensor includes an oscillator that has a circular or roughly circular shape and is supported by a mechanical support member, a fixed electrode that has a predetermined gap between the oscillator and the fixed electrode, and a drive electrode that is placed at a position different from the fixed electrode across the oscillator, and to which an AC drive voltage is applied to make the oscillator oscillate. In the voltage sensor, an electrostatic attractive force acts on the oscillator by applying a voltage to the fixed electrode, and a resonance frequency of the oscillator changes.