A switching device has a main IGFET having a Schottky barrier diode D3 for blocking an inverse current built therein, a protective switch means, and a protective switch control means. The protective switch means is connected in between a drain electrode D and a gate electrode G of the main IGFET. The protective switch control means turns on the protective switch means when an inverse voltage is impressed to the main IGFET. Thereby, the main IGFET is protected from the inverse voltage.