An electric power steering apparatus comprising: an electric motor that produces assist torque, based on steering torque produced by a driver of a vehicle; and a control unit (1a, 1b) that controls the electric motor, wherein the electric motor is provided with two sets of armature windings (2a, 2b) including a first armature winding and a second armature winding that are formed in the same manner, apart from being arranged in such a way as to be shifted by 120° electric angle, wherein the control unit (1a, 1b) is formed of two sets of control units that are formed with the same constituent members and that include a first control unit formed to be able of independently controlling the first armature winding and a second control unit formed to be able of independently controlling the second armature winding, wherein each of the first control unit and the second control unit has an input circuit (12a, 12b) to which information from a plurality of sensors is inputted, a driving circuit (11a, 11b) that generates a driving signal for driving the electric motor, an inverter circuit (3a, 3b) that is controlled by the driving signal, and a control circuit unit (4a, 4b) provided with a CPU (10a, 10b) that outputs a command signal for controlling the electric motor to the driving circuit (11a, 11b), based on the information inputted to the input circuit (12a, 12b), and wherein the CPU (10a, 10b) has an abnormality control mode in which when detecting an abnormality in part of the plurality of sensors, the CPU calculates a control amount that is different at least from a control amount at a normal time, in accordance with the sensor in which the abnormality has occurred and the contents of the abnormality, and then continues control of the electric motor; when control of the electric motor is continued in the abnormality control mode, a threshold value for detecting the abnormality is changed to a value different from a value at a normal time, in accordance with the contents of the control in the abnormality control mode, characterized in that the CPU (10a, 10b) calculates the threshold value to which the value at a normal time is changed, based on a mutual inductance between the first armature winding and the second armature winding. an electric motor that produces assist torque, based on steering torque produced by a driver of a vehicle; and a control unit (1a, 1b) that controls the electric motor, wherein the electric motor is provided with two sets of armature windings (2a, 2b) including a first armature winding and a second armature winding that are formed in the same manner, apart from being arranged in such a way as to be shifted by 120° electric angle, wherein the control unit (1a, 1b) is formed of two sets of control units that are formed with the same constituent members and that include a first control unit formed to be able of independently controlling the first armature winding and a second control unit formed to be able of independently controlling the second armature winding, wherein each of the first control unit and the second control unit has an input circuit (12a, 12b) to which information from a plurality of sensors is inputted, a driving circuit (11a, 11b) that generates a driving signal for driving the electric motor, an inverter circuit (3a, 3b) that is controlled by the driving signal, and a control circuit unit (4a, 4b) provided with a CPU (10a, 10b) that outputs a command signal for controlling the electric motor to the driving circuit (11a, 11b), based on the information inputted to the input circuit (12a, 12b), and an input circuit (12a, 12b) to which information from a plurality of sensors is inputted, a driving circuit (11a, 11b) that generates a driving signal for driving the electric motor, an inverter circuit (3a, 3b) that is controlled by the driving signal, and a control circuit unit (4a, 4b) provided with a CPU (10a, 10b) that outputs a command signal for controlling the electric motor to the driving circuit (11a, 11b), based on the information inputted to the input circuit (12a, 12b), and wherein the CPU (10a, 10b) has an abnormality control mode in which when detecting an abnormality in part of the plurality of sensors, the CPU calculates a control amount that is different at least from a control amount at a normal time, in accordance with the sensor in which the abnormality has occurred and the contents of the abnormality, and then continues control of the electric motor; when control of the electric motor is continued in the abnormality control mode, a threshold value for detecting the abnormality is changed to a value different from a value at a normal time, in accordance with the contents of the control in the abnormality control mode, characterized in that the CPU (10a, 10b) calculates the threshold value to which the value at a normal time is changed, based on a mutual inductance between the first armature winding and the second armature winding.