n this study, the application for monitoring atmospheric tritium at the site of nuclear fusion facility is presented. Construction and examination of the tritium sampler and its arrangement at the site are mainly discussed. Atmospheric tritium concentrations at Toki site were determined in the sampling period from September 2000 to June 2001. Although the data for HTO were low because of their low specific activity (0.62 Bq/l), our average HT and CH3T data were 9.1 and 3.3 mBq/m3, respectively, and systematically lower than the previously reported values at the same site, even if the considerable decay correction was carried out. Suitable monitoring points are discussed by considering the local meteorological features at the Toki site. Since the wind conditions at this site were governed by diurnal and nocturnal wind blowing to the contrary directions, it is concluded that the monitoring points should be placed at the site boundary of downwind direction of these winds. Considering that the expected levels of effluent tritium in the D-D experiment at the National Institute for Fusion Science are competitive with those in the environment, the detailed variations of the environmental tritium should be comprehended to detect minute amounts of the artificial tritium.