Activated carbons were prepared from Korean coal by steam activation in this study. The variation of pore structure of the activated carbons were investigated according to different carbonization temperatures. Yield, surface area, pore volume and pore structure of this activated carbon were compared with those of activated carbon prepared without carbonization. The investigated carbonization temperature ranged from 700℃ to 1,000℃. Carbonization was carried out in nitrogen atmosphere for 70 minutes and activation was performed by steam at 950℃ for 210 minutes. Surface area and pore volume of the resulting activated carbons increased with carbonization temperature. Also pore volume increased by 20% compared to the activated carbon without carbonization. Especially, in mesopore region, the activated carbon carbonized at 900℃ had more pores by 60% than that of activated carbon carbonized at other temperature.