Provided are an AP node to which a plurality of sensors is connected; and a DB node connected to the AP node. The AP node includes: a receiving unit configured to receive measurement data including values of a plurality of measurement items output from each of the sensors; a queue that stores a most recent value in units of measurement items of each of the sensors; a determination unit configured to refer to the queue and then determine whether the value of each of the measurement items has changed, every time the measurement data is output from each of the sensors; a transmission unit configured to, in a case where there is a measurement item having a value change, generate storage data including the value of the measurement item for each of the measurement items and transmit the generated data to the DB node; and an overwriting unit configured to overwrite the most recent value in the queue with a newest value of the measurement item. The DB node includes: a plurality of tables that stores a value included in the measurement data for each of the measurement items of each of the sensors; and a storing unit configured to store the storage data transmitted from the AP node in a corresponding table.