In order to examine the ability of a simple device to measure the atmospheric carbon dioxide（CO2）, we carried out a continuous measurement of CO2 concentrations in Kumamoto City. The obtained data indicates the diurnal and seasonal variations clearly. Typical diurnal variation is as follows: the highest concentration is recorded at just before the sunrise, and after that the concentrations decrease during the daytime, and then it increase after the sunset. We found that three patterns of the diurnal variation as follows: [1] typical diurnal variation with a sharp concentration peak [2] typical diurnal variation with broad concentration peak, [3] keeping the lower concentrations all-day. Furthermore, it was found that the obtained CO2 concentrations change is related with daylight and wind. These results suggest that the simple device used here is useful to obtain the CO2 data as teaching materials at the community area where pupils live.