To provide a network environment monitoring device by which many temperature sensors are connected with one port, wiring does not become complicated, which is hard to be influenced by voltage drop and noise even when wiring distance is long, with high data precision, length of the entire wiring is shorten and cost is reduced.

A network environment monitoring device 1 connects a temperature sensor 2 of digital output by two pieces of electric wire 3. Since crossover connection is performed to the temperature sensor 2 and another sensor 2 by two lines of electric wire 3 and each temperature sensor separately has an identification ID, measurement data is made identifiable from that of another temperature sensor 2.