Power supply current is supplied to a plurality of electric loads, the power supply current being generated by a DC power supply, flowing in and branching from a shared power supply switching device and then flowing in reverse connection protection devices that are a field-effect transistor and connected in series to the electric loads, respectively. The reverse connection protection devices are connected in a polarity such that the power supply current flows in the forward direction of parasitic diodes generated between the source terminal S and the drain terminal D of the field-effect transistor. When the current in the field-effect transistor is less than a predetermined value, a gate control circuit interrupts the gate voltage of the reverse connection protection device to cause the reverse connection protection device to open.