It is among the currently most important problems that the ozone layer continues to be eroded to disappear. The ozone layer is possibly destroyed by NO produced from N2O as well as chlorofuloro carbons (CFCs). In addition, N20 in the atmosphere contributes to the greenhouse effect more significantly than C02 gas per molecule. This paper reports the results of FFT(Fast Fourier Transform) analysis and Folding analysis from continuous monitoring data at Nagoya University from January 1st to December 31st in 1996. The results show 1/f dependence together with 1.0 day periodicity and 2−5 day periodic structure. The former indicates an effect of human activities and the latter shows a characteristic eddy diffusion size scale of several hundred meters.