An actuator control apparatus includes: an actuator that changes a state amount of an internal combustion engine; a sensor that detects an actual operation position of the actuator; a controller that controls the actuator to bring the actual operation position of the actuator to a target operation position set based on the operation state of the internal combustion engine; and a diagnosis portion that diagnoses the operation state of the actuator to be normal if the deviation between the target operation position and the actual operation position has been small for a predetermined time period and the amount by which the target operation position has changed in the predetermined time period is equal to or larger than a predetermined value. A method for controlling such an actuator control apparatus is also provided.