An adaptive control apparatus that adaptively controls directivity of an array antenna is disclosed. The adaptive control apparatus that can be used by a radio apparatus and a receiver includes a setting unit configured to set up parameters such as the distance between the radio apparatus and the receiver that receives a radio frequency signal transmitted by the radio apparatus, the relative moving speed, and the moving direction of the receiver in reference to the radio apparatus. The adaptive control apparatus further includes an evaluating unit configured to evaluate how much received power at the receiver or the radio apparatus changes after a predetermined period, and a weight control unit configured to adjust two or more weighting factors about two or more antenna elements that constitute the array antenna. The directivity of the array antenna is controlled such that the amount of change of the received power is kept within fixed limits independent of the distance between the receiver and the radio apparatus.