A steering control apparatus, comprising: control processing circuits (310, 320) configured to control driving of a motor that is a source of power for turning a steered wheel of a vehicle so that the power is applied to a steering mechanism; and a plurality of communication lines (C1, C2) for communicating control information necessary for the control processing circuits (310, 320) to control the driving of the motor, the plurality of communication lines being connected to each of the control processing circuits (310, 320), wherein the plurality of communication lines include: a main communication line for communicating main control information (ADAS1*) that is set so as to be mainly used by the control processing circuits (310, 320) as the control information; and a subsidiary communication line for communicating subsidiary control information (ADAS2*) that is structured so as to be usable by the control processing circuits (310, 320) as the control information in place of the main control information (ADAS1*), characterized in that the steering control apparatus further includes an abnormality detecting circuit configured to detect, as a communication state of each of the plurality of communication lines (C1, C2), a normal state in which the control information is communicable, a semi-normal state detected during the normal state, the semi-normal state being a state in which an abnormality occurs but the control information is communicable, or an abnormal state detected during the semi-normal state, the abnormal state being a state in which an abnormality occurs and the control information is not communicable, and the abnormality detecting circuit is configured to: when the normal state is detected for the main communication line, set use of the main control information (ADAS1*) communicated via the main communication line; and when the semi-normal state or the abnormal state is detected for the main communication line, set use of the subsidiary control information (ADAS2*) communicated via the subsidiary communication line under a condition that the normal state is detected for the subsidiary communication line. control processing circuits (310, 320) configured to control driving of a motor that is a source of power for turning a steered wheel of a vehicle so that the power is applied to a steering mechanism; and a plurality of communication lines (C1, C2) for communicating control information necessary for the control processing circuits (310, 320) to control the driving of the motor, the plurality of communication lines being connected to each of the control processing circuits (310, 320), wherein the plurality of communication lines include: a main communication line for communicating main control information (ADAS1*) that is set so as to be mainly used by the control processing circuits (310, 320) as the control information; and a subsidiary communication line for communicating subsidiary control information (ADAS2*) that is structured so as to be usable by the control processing circuits (310, 320) as the control information in place of the main control information (ADAS1*), characterized in that a main communication line for communicating main control information (ADAS1*) that is set so as to be mainly used by the control processing circuits (310, 320) as the control information; and a subsidiary communication line for communicating subsidiary control information (ADAS2*) that is structured so as to be usable by the control processing circuits (310, 320) as the control information in place of the main control information (ADAS1*), characterized in that the steering control apparatus further includes an abnormality detecting circuit configured to detect, as a communication state of each of the plurality of communication lines (C1, C2), a normal state in which the control information is communicable, a semi-normal state detected during the normal state, the semi-normal state being a state in which an abnormality occurs but the control information is communicable, or an abnormal state detected during the semi-normal state, the abnormal state being a state in which an abnormality occurs and the control information is not communicable, and the abnormality detecting circuit is configured to: when the normal state is detected for the main communication line, set use of the main control information (ADAS1*) communicated via the main communication line; and when the semi-normal state or the abnormal state is detected for the main communication line, set use of the subsidiary control information (ADAS2*) communicated via the subsidiary communication line under a condition that the normal state is detected for the subsidiary communication line. when the normal state is detected for the main communication line, set use of the main control information (ADAS1*) communicated via the main communication line; and when the semi-normal state or the abnormal state is detected for the main communication line, set use of the subsidiary control information (ADAS2*) communicated via the subsidiary communication line under a condition that the normal state is detected for the subsidiary communication line.