Global warming may cause serious changes in global climate. Estimating the amount of greenhouse gases (GHGs) exchange between the atmosphere and ground surfaces is required to reduce the net emission. Of all the GHGs, methane (CH₄) and nitrous oxide (N₂O), which have strong global warming potentials, are mainly emitted from agricultural ecosystems. For example, CH₄ emitted in Japan was mainly from rice paddy fields. Additionally, because of the report that large emission was observed after fertilization, intensive agriculture is suggested to be one of the sources of the N₂O. GHGs are often emitted suddenly with changes in soil and atmospheric conditions. For example, CH₄ gas generated by microbiological activities accumulates in the submerged soil, and is emitted suddenly from the soil surface when air pressure decreases. Therefore, continuous measurements of GHGs fluxes are needed for more accurate estimation of gases exchanges. We made the system of continuous gas-flux measurement using the relaxed eddy accumulation (REA) method. We will present the results of continuous CH₄ and N₂O fluxes and the surface and soil condition such as radiation, air and soil temperatures, oxidation-reduction potential (ORP), and water content in the paddy field of central Japan to discuss the relationship between gas exchange and soil environment.