We operated a Hall sensor using energy harvested from a magnetic wire. A batteryless sensor is expected to be a key device for the Internet of Things. Magnetization reversal in magnetic wires with bistable magnetization states induces a pulse voltage in a pickup coil. The amplitude of the voltage is independent of the applied field frequency, down to zero. This fast magnetization reversal is accompanied by a large Barkhausen jump, which has been known as the Wiegand effect. Electricity generation using this effect, obtained with twisted FeCoV magnetic wires, was studied. The energy obtained as a single pulse voltage was 600 nJ. The Hall sensor operated with this pulse voltage. The pulse power of 0.88 V/1.3 mA was applied to the Hall sensor. The Hall voltage was proportional to the sensing magnetic field of 50–300 mT.