An electric power steering apparatus, comprising: an electric motor configured to rotate a steering mechanism of a vehicle; a control unit, which is configured to drive the electric motor, and includes a CPU and a plurality of power supply circuits (13, 14); and a power supply control circuit configured to output a stop signal for individually stopping output functions of the plurality of power supply circuits (13, 14) based on a result of reading an input voltage supplied in common to the plurality of power supply circuits (13, 14), the plurality of power supply circuits (13, 14) including: a first power supply circuit configured to generate from the input voltage a first output voltage to be supplied to a circuit other than the CPU; and a second power supply circuit configured to generate from the input voltage a second output voltage to be supplied to the CPU included in the control unit, wherein the first output voltage is higher than the second output voltage, wherein the power supply control circuit has at least three voltage sub-ranges being an upper level voltage sub-range, an intermediate level voltage sub-range, and a lower level voltage sub-range obtained by dividing a range of the input voltage, the at least three voltage sub-ranges being preset in accordance with a requirements specification, and wherein the power supply control circuit is configured to control the first power supply circuit and the second power supply circuit by, in accordance with the result of reading the input voltage, outputting the stop signal to both the first power supply circuit and the second power supply circuit when the input voltage falls within the lower level voltage sub-range, outputting the stop signal to the first power supply circuit when the input voltage falls within the intermediate level voltage sub-range, and preventing the stop signal from being output when the input voltage falls within the upper level voltage sub-range. an electric motor configured to rotate a steering mechanism of a vehicle; a control unit, which is configured to drive the electric motor, and includes a CPU and a plurality of power supply circuits (13, 14); and a power supply control circuit configured to output a stop signal for individually stopping output functions of the plurality of power supply circuits (13, 14) based on a result of reading an input voltage supplied in common to the plurality of power supply circuits (13, 14), the plurality of power supply circuits (13, 14) including: a first power supply circuit configured to generate from the input voltage a first output voltage to be supplied to a circuit other than the CPU; and a second power supply circuit configured to generate from the input voltage a second output voltage to be supplied to the CPU included in the control unit, a first power supply circuit configured to generate from the input voltage a first output voltage to be supplied to a circuit other than the CPU; and a second power supply circuit configured to generate from the input voltage a second output voltage to be supplied to the CPU included in the control unit, wherein the first output voltage is higher than the second output voltage, wherein the power supply control circuit has at least three voltage sub-ranges being an upper level voltage sub-range, an intermediate level voltage sub-range, and a lower level voltage sub-range obtained by dividing a range of the input voltage, the at least three voltage sub-ranges being preset in accordance with a requirements specification, and wherein the power supply control circuit is configured to control the first power supply circuit and the second power supply circuit by, in accordance with the result of reading the input voltage, outputting the stop signal to both the first power supply circuit and the second power supply circuit when the input voltage falls within the lower level voltage sub-range, outputting the stop signal to the first power supply circuit when the input voltage falls within the intermediate level voltage sub-range, and preventing the stop signal from being output when the input voltage falls within the upper level voltage sub-range.