A semiconductor device, including a power supply terminal, an output terminal, a ground terminal, an N-channel main MOSFET connected between the power supply terminal and the output terminal, a drive circuit which operates to drive the main MOSFET, using a potential difference, between the power supply terminal and an internal ground, as a power supply thereof, an internal ground generation circuit which is provided between the power supply terminal and the ground terminal and which generates the internal ground, an N-channel first MOSFET provided between an output terminal of the internal ground generation circuit and the ground terminal, and a low voltage detection circuit which is provided between the power supply terminal and the ground terminal, and which turns on the first MOSFET upon detecting that a voltage between the power supply terminal and the ground terminal drops below a prescribed voltage.