Global climate change is an important issue for human beings. A major contributor for the global climate change may be increasing greenhouse gases. Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) are considered as major greenhouse gases in agricultural land. In particular, a flooded rice paddy field is a major source of atmospheric CH₄. On the contrary, non-flooded rice soils, after drainage or during fallow period, are able to act as a sink for CH₄. There is a little information about CH₄ uptake from non-flooded rice fields. Recently, micrometeorological techniques for measuring trace gas flux have progressed. Gas fluxes obtained with micrometeorological techniques represent spatially integrated fluxes in a macro-scale; therefore, the techniques provide sufficient site special representations. In addition, a measuring system doesn’t disturb environmental conditions during measurement. Eddy-covariance technique (EC) is a popular and reliable micrometeorological technique. The EC requires a sensor whose response time must be sufficiently small to detect fluctuation of a gas concentration on the order of 10Hz to measure gas flux. The recent advances in laser spectroscopy enable researchers to measure trace gas concentrations such as CH₄ at fast sampling rates of 10Hz. The objective of this study is to investigate gas (CH₄, CO₂, H₂O) fluxes in a rice paddy field during a fallow period using EC. Field experiments will be conducted in a rice paddy field, Japan. Gas (CH₄, CO₂, H₂O) fluxes will be continuously measured using EC. Gas concentrations (CH₄, CO₂, H₂O) will be analysed by a closed-path gas analyser (G2301-f, Picarro Inc., USA) based on wavelength-scanned cavity ring-down spectroscopy (WS-CRDS). CO₂ and H₂O will be also analysed by an open-path infrared gas analyser (EC150, Campbell Inc., USA). Results will be discussed.