When a current input to a step-up voltage device of an electric power steering apparatus is equal to or higher than a first threshold current and an input voltage applied to the step-up voltage device is lower than a first threshold voltage, the step-up voltage device of the electric power steering apparatus discontinuously switches an output voltage to a voltage lower than a rated step-up voltage. When the input voltage becomes lower than a second threshold voltage which is lower than the first threshold voltage, the step-up voltage device sets the output voltage to a voltage equal to the input voltage.