A sensor net system including: a sensor node which includes: a sensor which obtains sensor data of a worker; a radio frequency circuit which notifies a server of the sensor data; and a server which includes: a relation list for correlating the sensor data with work status of the worker; a unit for confirming the work status of the worker based on the obtained sensor data by using the relation list; a unit for displaying the confirmed work status on a display unit connected to the server.