The present invention provides a switching device capable of further minimizing the ON resistance of a switching element. Switching element has field application electrode that is connected to semiconductor substrate with insulating film interposed therebetween. Field control unit of driving unit is connected to field application electrode and source electrode of switching element, and applies a bias voltage Ve between field application electrode and source electrode. Field control unit applies an electric field from field application electrode to a hetero-junction interface of semiconductor substrate, by applying the bias voltage Ve exceeding a threshold value to switching element. In short, in the ON state of switching element, the electric field that is applied from field application electrode to semiconductor substrate works to increase electron concentration in a channel region by a field effect and decrease the ON resistance of switching element.