A sensor node (101-1) has no subsequent assignment-destination sensor node (101), when the execution of data processing is assigned to a sensor node (101-h) that can directly communicate with a parent device (102) (dashed-lined arrow), and the data processing is not completed by the assignment-destination sensor node (101-h). Thus, when unable to execute the data processing, the sensor node (101-1) requests a sensor node (101-m) that requires plural hops in communicating with the parent device (102) (solid lined arrow). Even when the data processing is not completed by the assignment-destination sensor node (101-m), the data processing can be completed by executing the data processing in stages by plural sensor nodes (101).