An inverter detects whether a fault that an over current is supplied to a load is generated when the inverter supplies AC power and operates the load, and uses a voltage between a collector and an emitter of a switching element for detecting whether an over current is supplied to the load. The inverter cuts off a switching control signal, switches DC power by a plurality of switching elements supplying AC power to the load, detects the generation of the fault by a plurality of fault detecting units using the voltage of both ends of the collector and the emitter of a plurality of switching elements, generates the switching control signal by a controlling unit that outputs the switching control signal to a switching operation unit, and detects the generation of a fault by any of the plurality of fault detecting units.