A semiconductor device includes a first circuit operating with a first potential as a reference potential and a second circuit operating with a second potential different from the first potential as a reference potential, able to reliably detect that a negative voltage is applied to the first circuit. The first circuit includes a current source. The current source supplies a current to the low side circuit, and changes the current in response to whether or not the first potential becomes a negative voltage with respect to the second potential. Also, the second circuit includes a negative voltage detection circuit. The negative voltage detection circuit monitors a change in the current supplied from the current source and detects that a negative voltage is applied to the high side circuit.