To provide a servo controller that has high disturbance suppressing capability and that performs smooth control irrespective of feedback speed of a motor, and to provide its control method.

The servo controller comprises a speed controller 1, a power converter 2, an observer 5, a first filter 6, a second filter 7, and an adder 8. A signal obtained by adding a signal created by filtering with the first filter 6 an estimated speed Vfb^ outputted from the observer and a signal created by filtering a speed detection value Vfb with the second filter 7 is used as a speed feedback Vfb2 that is used by the speed controller 1.