A management server 103 holds a parameter of a sensor device 101 and change management information related to a change in the parameter, and transmits the changed parameter and the change management information to the sensor device. The sensor device 101 holds the parameter and the change management information transmitted from the management server, and transmits the change management information to the management server together with measurement data. The management server collates the received change management information and preliminarily-held change management information to determine the change in the parameter on the basis of a result of the collation.