In a feedback control apparatus comprising a controller, a control object to be controlled by the controller, and an observer for inputting a control output from the control object and an output of the controller and setting an output of a control object model to be a feedback signal, the observer includes an observer compensator for inputting a difference between the control output and an output of an element model and inputs, to the control object model, a sum of an output of the observer compensator and the output of the controller. Consequently, a control system having an excellent response performance can be constituted and a stable observer can easily be constituted.