The effect of microwave treatment on Korean ginseng was studied by measuring the changes in moisture, crude lipid, crude ash, crude protein, total dietary fiber and saponin contents, as well as changes in density, color and microstructure. Korean ginseng was treated with 100 or 200 watts of microwaves for 1 or 3 hrs, respectively, followed by drying using an oven at 60℃ for 96 hrs. The moisture contents decreased to 13.12~10.77% from an initial 76.26%. The amounts of lipid and ash were reduced in proportion to the time of microwave treatment and level of microwave power. The amount of protein in ginseng after microwave treatment did not significantly change. The amount of total dietary fiber increased after microwave treatment and the color of dried ginseng became dark. The amounts ofginsenoside-Rb1, Rb2+Rb3, Rc, Rd, Re, Rf, Rg1, Rg2+Rh1 and Rg3 were reduced after treatment with 100 watts of microwave radiation for 1 and 3. The amounts ofginsenoside-Rb1, Rd, Re, Rf, Rg1, Rg2+Rh1 and Rg3 after treatment with 200 watts of microwave radiation for 1 and 3 hr also reduced. On the other hand, the amounts ofginsenoside-Rb2+Rb3 and Rc after treatment of ginseng with 200 watts of microwave radiation for 1 and 3 hrs were increased.