A reception unit receives signals from a plurality of radio terminals. A transmission unit transmits signals to the radio terminals. A direction determination unit determines the directions of the radio terminals viewed from the transmission unit on the basis of the signals received by the reception unit. A group selection unit distributes, by using a threshold, the transmission powers or downlink data transmission rates of radio terminals which transmit signals in a time-overlapping manner, thereby classifying the radio terminals into two groups. Then, the group selection unit selects a group having a smaller total number of radio terminals. A directivity pattern control unit controls a directivity pattern on the basis of the directions of the radio terminals determined by the direction determination unit.