Abstract: A control apparatus of an electric power steering apparatus capable of firmly detecting an abnormality of a torque detection value, caused by a drift occurred in a torque sensor and by a connector contact resistor, with a simple arrangement. A current supplied from a power supply flows through a potentiometer (3A) of a torque sensor (3), this current is supplied to a current detecting resistor (13g), a drift occurred in the torque sensor (3) is detected by a voltage across terminals of this resistor, the detected drift detection voltage V.sub.is is read in a microcomputer (21), and the drift detection voltage V.sub.is is compared with a set value to judge as to whether or not the drift is present within a normal range. The torque sensor is constructed of a main potentiometer (3.sub.M) and a sub-potentiometer (3.sub.S). A change amount .DELTA.V.sub.M is calculated from a difference between a presently detected value and a previously detected value of the torque detection voltage V.sub.