A semiconductor device includes m power transistors (m is an integer of 2 or more) coupled in parallel each of which has a sense source terminal, a Kelvin terminal and a source terminal, a first average circuit that connects the first resistor and the second resistor in order between the sense source terminal and the Kelvin terminal and generates first to fourth average voltages and an arithmetic circuit that measures a first current value flowing through the sense source terminal from the first and second average voltages, measures a second current value flowing through the sense source terminal from the third and fourth average voltages and measures a current value flowing through the source terminal from the first to fourth average voltages and the first and second current values.