The average of daily ozone concentration at the surface was 60~70 ppb during soybean growth period(June ~ August) in 2004 and 2005. This ozone level during growth period is estimated to decrease soybean yield by 15% according to previous studies. After soybean plant was exposed to O3 of 200 ppb level in the chamber for 3 hours, photosynthetic rate decreased by 35% and transpiration decreased by 50%. The fluorescence ratio(Fv/Fp) decreased as O3 concentrations increase. It was obsered by SEM that guard cell and epidermal tissue was damaged greatly in 100 and 200 ppb level and necrotized entirely in 300 ppb level. In O3 treatment of 5 soybean test cultivars, Daewonkong, Cheongjakong were tolerant and Jinpumkong, Dawonkong were susceptible in specific leaf weight, relative water contents in leaf and greeness of leaves. The specific leaf weight in response to O3 treatment increased so much in Taekwangkong, Daewonkong and Cheongjakong but decreased so much according to O3 concentration increase in Dawonkong.Relative water contents in leaf decreased gradually according to O3 concentration increase in all test cultivars. But the degree of decrease was much less in Daewonkong and Cheongjakong than Jinpumkong and Dawonkong. The similar tendencies were showed in the changes of greeness of leaves according to days after O3 treatment.