Paclitaxel is produced by various species of yew trees and has been extensively used to treat tumors. In our research, a taxadiene synthase (TS) gene from Taxus brevifolia was used to transform the roots of cultured ginseng (Panax ginseng C.A. Meyer) to produce taxadiene, the unique skeletal precursor to taxol. The TS gene was successfully introduced into the ginseng genome, and the de novo formation of taxadiene was identified by mass spectroscopy profiling. Without any change in phenotypes or growth difference in a TS-transgenic ginseng line, the transgenic TSS3-2 line accumulated $9.1{mu}g$ taxadiene per gram of dry weight. In response to the treatment of methyl jasmonate for 3 or 6 days, the accumulation was 14.6 and $15.9{mu}g$ per g of dry weight, respectively. This is the first report of the production of taxadiene by engineering ginseng roots with a taxadiene synthase gene.