A control device for a motor which turns turning wheels of a vehicle and which includes a first coil (14) and a second coil (14) insulated from each other, the control device comprising: a first circuit (30) that calculates a first amount (MV) of operation corresponding to a torque which is generated by the motor to feedback-control an angle which is able to be converted to a turning angle of the turning wheels and which is detected by a first sensor (40) such that the angle becomes a target angle which is calculated by an external circuit and controls supply of electric power to the first coil based on a value (MS) which is obtained by dividing the first amount (MV) of operation according to the number of control systems; and a second circuit (30) that calculates a second amount (MV) of operation corresponding to the torque which is generated by the motor to feedback-control an angle detected by a second sensor (40) such that the angle becomes the target angle and controls supply of electric power to the second coil based on a value (MS) which is obtained by dividing the second amount of operation according to the number of control systems, characterized in that the external circuit generates an instruction for performing a process of increasing an amount of operation which is calculated by one of the first circuit and the second circuit according to the number of control systems when the other of the first circuit and the second circuit fails, the control device further comprises a monitoring circuit that monitors at least whether an abnormal state of a source voltage (VB, VB) of the first circuit and the second circuit is maintained for a set time, the first circuit and the second circuit increase an amount of operation of one of the first circuit and the second circuit according to the number of control systems when it is recognized that the other of the first circuit and the second circuit fails based on a result of monitoring from the monitoring circuit, the monitoring circuit also monitors mutual communication between the first circuit and the second circuit, and the first circuit and the second circuit do not employ the instruction when the instruction is generated and it is recognized that the mutual communication between the first circuit and the second circuit is normal based on the result of monitoring. a first circuit (30) that calculates a first amount (MV) of operation corresponding to a torque which is generated by the motor to feedback-control an angle which is able to be converted to a turning angle of the turning wheels and which is detected by a first sensor (40) such that the angle becomes a target angle which is calculated by an external circuit and controls supply of electric power to the first coil based on a value (MS) which is obtained by dividing the first amount (MV) of operation according to the number of control systems; and a second circuit (30) that calculates a second amount (MV) of operation corresponding to the torque which is generated by the motor to feedback-control an angle detected by a second sensor (40) such that the angle becomes the target angle and controls supply of electric power to the second coil based on a value (MS) which is obtained by dividing the second amount of operation according to the number of control systems, characterized in that the external circuit generates an instruction for performing a process of increasing an amount of operation which is calculated by one of the first circuit and the second circuit according to the number of control systems when the other of the first circuit and the second circuit fails, the control device further comprises a monitoring circuit that monitors at least whether an abnormal state of a source voltage (VB, VB) of the first circuit and the second circuit is maintained for a set time, the first circuit and the second circuit increase an amount of operation of one of the first circuit and the second circuit according to the number of control systems when it is recognized that the other of the first circuit and the second circuit fails based on a result of monitoring from the monitoring circuit, the monitoring circuit also monitors mutual communication between the first circuit and the second circuit, and the first circuit and the second circuit do not employ the instruction when the instruction is generated and it is recognized that the mutual communication between the first circuit and the second circuit is normal based on the result of monitoring.