A load driving device supplies power to drive a solenoid valve from a high-voltage power source via a discharge MOSFET or from a direct current power source via a constant-current MOSFET. A return current flows through a reflux MOSFET. A control circuit determines an operation state of the reflux MOSFET by detecting a drain voltage of the reflux MOSFET as a detection voltage. When the reflux MOSFET does not turn ON due to a gate-ground fault, the return current flows through a parasitic diode and the control circuit can determine such a fault based on the detection voltage.