1. A robot control apparatus comprising: an actuator for rotatably driving a driving shaft of an arm; a generator unit configured to generate target positional data of an end of the arm; a first detection unit to detect a rotation angle of the driving shaft at each sampling period; a first computation unit configured to compute current positional data of the end of the arm using the rotation angle; a second computation unit configured to compute an input value relating to the actuator, by using the target positional data and the current positional data; a third computation unit configured to compute an estimation value of a driving torque for driving the actuator using a rotation angle of the driving shaft; a fourth computation unit configured to compute a difference between the estimation value of the driving torque and a true value of the driving torque relating to the input value; and a second detection unit to detect a disturbance applied to the arm, wherein the second detection unit includes an update unit configured to estimate a set of parameter of a time-series model by setting the difference as a variable and updating the time-series model of the first sampling period by applying the set of the parameter, and a determination unit configured to determine whether or not a disturbance occurs in the arm, by comparing the time-series model of the first sampling period with a time-series model of a second sampling period preceding the first sampling period.