Reductions in the ozone column have led to substantial increase in UV-B radiation at the Earth's surface with the amount and intensity dependent on atmospheric and geographic factors. Our objectives were to understand the effect of UV-B radiation on photosynthesis and carbohydrate synthesis of soybean, and to establish an indicator to select resistant soybean cultivar against UV-B radiation. Soybean seeds (cv. Daepungkong) were sown and grown for 4 weeks in an environmentally controlled chamber. UV-B radiation was delivered to plants for four hours, each day, from 10:00 to 14:00 h by five fluorescent UV lamps. A distance of 1 m from lamps to the top of plants was always maintained throughout the experiment. The biologically effective UV-B radiation level was 21.6 kJ m-2 d-1 using the generalized plant responses action spectrum normalized at 300 nm. The damage of soybean leaves was optically observed at the second day of UV-B radiation, and leaf veins were first injured. Photosynthetic rate was reduced after 2 days of UV-B radiation, and, at 5 days, it was a half level (6.3 μmol m-2 s-1) compared with control (12.1 μmol m-2 s-1). UV-B radiation led to the reduction of stomatal conductance around 5 days of treatment. The decrease in stomatal conductance means the reduction of leaf transpiration and the influx of carbon dioxide. Also, the reduction of photosynthetic rate caused an accumulation of the intercellular carbon dioxide. It is suggested that photosynthetic characteristics can be used an indicator to select UV-B-resistant soybean cultivar.