1. An actuator control device for force-controlling a joint driving actuator according to a commanded joint force command value τ a , the actuator control device comprising: a joint value detecting means for detecting a joint value q at an output stage of the actuator; an action force detecting means for detecting an action force τ e in a joint driving direction at the output stage of the actuator; and a driving force determining means for determining an instructed driving force τ to the actuator, on the basis of an ideal response model of the actuator which specifies the relationship of a joint value acceleration target value achieved as the actuator responds ideally when the joint force command value τ a , the action force τ e , and a joint value velocity obtained by time-differentiating the joint value q are given.