A wireless sensor network system comprising: a plurality of sensor devices (11, 12) 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, wherein the wireless sensor network system wirelessly connect the plurality of sensor devices to the information gathering apparatus, each sensor device includes a transmitter to transmit a transmission request for connecting to the information gathering apparatus, and 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 at least one of setting the adaptive array antenna to be non-directional and changing a directivity of the adaptive array antenna, and that receives a signal transmitted from at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and a connected sensor device; and a second directivity-changing section to change the directivity of the adaptive array antenna in accordance with a reception state of the signal transmitted from the at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and the connected sensor device, wherein the each sensor device includes an incorporating section to incorporate a transmission request from another sensor device into a signal being transmitted from the each sensor device upon receiving the transmission request from the another sensor device, and to transmit the signal to the information gathering apparatus, and the information gathering apparatus includes a retrieving section to retrieve a new transmission request from the unconnected sensor device included in the signal transmitted from the connected sensor device. a plurality of sensor devices (11, 12) 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, wherein the wireless sensor network system wirelessly connect the plurality of sensor devices to the information gathering apparatus, each sensor device includes a transmitter to transmit a transmission request for connecting to the information gathering apparatus, and 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 at least one of setting the adaptive array antenna to be non-directional and changing a directivity of the adaptive array antenna, and that receives a signal transmitted from at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and a connected sensor device; and a second directivity-changing section to change the directivity of the adaptive array antenna in accordance with a reception state of the signal transmitted from the at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and the connected sensor device, a first directivity-changing section that, when the information gathering apparatus receives a transmission request from an unconnected sensor device, performs at least one of setting the adaptive array antenna to be non-directional and changing a directivity of the adaptive array antenna, and that receives a signal transmitted from at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and a connected sensor device; and a second directivity-changing section to change the directivity of the adaptive array antenna in accordance with a reception state of the signal transmitted from the at least one of (a) the unconnected sensor device and (b) the unconnected sensor device and the connected sensor device, wherein the each sensor device includes an incorporating section to incorporate a transmission request from another sensor device into a signal being transmitted from the each sensor device upon receiving the transmission request from the another sensor device, and to transmit the signal to the information gathering apparatus, and the information gathering apparatus includes a retrieving section to retrieve a new transmission request from the unconnected sensor device included in the signal transmitted from the connected sensor device.