A semiconductor device is provided, which has a wide-bandgap semiconductor element, such as a SiC element, and which includes a sensor capable of responding sufficiently to characteristic requirements for protecting and controlling the semiconductor element. The semiconductor device includes a wide-bandgap semiconductor element mounted on a substrate; and a light-receiving element that receives light emitted from the wide-bandgap semiconductor element when the wide-bandgap semiconductor element is in a conduction state.