Temperature dependence of soil CO₂ flux and CO₂ production and consumption were investigated in the vadose zone of Arakawa Lowland in the Tokyo Metropolitan area of Japan. Investigations were based on the combined techniques of a closed chamber method for measuring CO₂ emission, frequent monitoring of the soil CO₂ concentration profile through the upper meter of the soil, and laboratory measurements of soilgas diffusivity for sampled, intact soil cores. Emission of CO₂ from the vadose zone to the air was measured during a monitoring period of 2 years and 8 months. The soil surface CO₂ flux increased with increasing soil temperature at 10 cm depth in two monitoring points located at about 10-m distance to each other. Calculated 𝑄₁₀ values defined as the increase in soil surface CO₂ flux per 10°C increase in soil temperature were approximately 2, at the two monitoring points. Approximately 90% of the emitted CO₂ was produced at surface soil layer.