A wireless sensor network system includes a plurality of sensor devices each having a non-directional antenna, and an information gathering apparatus having an adaptive array antenna and gathering information detected by the plurality of sensor devices. Each sensor device includes a transmitter to transmit a transmission request for connecting to the information gathering apparatus. The information gathering apparatus includes, a first directivity-changing section that, when the information gathering apparatus receives a transmission request from an unconnected sensor device, performs one of changing the adaptive array antenna to be non-directional, and changing a directivity of the adaptive array antenna, and that receives a signal transmitted from one of the unconnected sensor device and the unconnected sensor device and a connected sensor device, and a second directivity-changing section to change the directivity in accordance with a reception state of the signal.