To provide an environment monitoring support system reducing communication cost, and simplifying display of information related to pollutant to reduce the work load, with respect to an operator of a monitoring station.

A decision processing part 38 of an observation device 20(i) acquires observation data, outputted from a sensor via a basic control part 34 and an input part 36. The decision processing part 38 compares the inputted observation data and a prescribed criterion condition, and outputs a decision result thereof to a transmission control part 40. In this case, the decision processing part 38 compares the observation data with at least one condition of whether missing measurement is absent in the observation data, whether the observation data are within a measurement range of the sensor, and whether the observation data are within a range of an environmental criterion, and decides whether the observation data are data satisfying the criterion condition. The decision result thereof is transmitted to the monitoring station via radio 16.