An electric power steering apparatus includes a shunt resistor connected to an inverter, a controlling motor current detection circuit connected to two terminals of the shunt resistor in a positive direction, which detects phase currents of a motor and uses the detected phase current as a controlling motor current detection value of assist control, and a diagnostic motor current detection circuit that is connected to two terminals of the shunt resistor in an opposite direction and detects a failure of the controlling motor current detection circuit. Each phase current of the motor is detected by one-shunt type and the assist control is performed, and two systems of a circuit for amplifying a voltage between two terminals of the shunt resistor are provided.