A disclosed base station apparatus for a mobile communication system includes a collection unit collecting measured data from one or more user equipment terminals with respect to each direction of arrival, the measured data including at least quality information of a downlink signal, a conversion unit converting the measured data into an evaluation value in accordance with a predetermined evaluation function, a deriving unit deriving a weight update amount determining directivity based on an angular distribution of the plural evaluation values, and a transmission unit transmitting a downlink signal weighted based on the weight update amount.