Measuring devices are connected to the same network. A sharing control processing unit controls sharing of capture of packets among the measuring devices. An aggregating unit collects the captured packets. Each measuring device notifies the sharing control processing unit of a state about its capture. The sharing control processing unit determines which measuring device is to start/stop the capture, according to a predetermined rule and the notified state. When determining that the capture is to be switched from a first measuring device to a second measuring device, the sharing control processing unit instructs the second measuring device to start the capture. After receiving a notification that the second measuring device has actually captured a packet(s), the sharing control processing unit instructs the first measuring device to stop the capture. The aggregating unit identifies a duplicate packet(s) double captured by the first and second measuring devices, and reconstructs the packets.