We newly developed a technique of radiation thermometry using a Sony’s consumer digital camcorder. Our system is not only convenience and cost effective but with a better performance than previous infrared thermometers, particularly in the place like a crater of volcano where is abundant in gas. This is because our system uses the submicron wavelength band, in which radiation is less influenced by absorption of gas than in the thermal infrared wavelength (>3 μm). We carried out observations of red glow at Aso volcano and succeeded in measuring the temperature of about 800°C, which is much more acceptable than previously reported values of 200–400°C. When we measure the temperature of about 300–700°C and 600–900°C in the place where is abundant in gas, using the camcorder with the near-infrared and with the visible wavelength mode is better than the thermal infrared region, respectively.