The soybean aphid, Aphis glycines Matsumura, was introduced about a decade ago from Asia into North America where it has become a serious pest of soybeans. This invasive pest has rapidly spread throughout the midwestern United States and southern Canada since 2000. We examined 689 individuals obtained from 23 different collections in USA, Korea, China and Japan for testing eight microsatellite loci. To estimate the relative likelihood of alternative introduction scenarios of the soybean aphid, an approximate Bayesian computation (ABC) was performed for microsatellite data as implemented in DIYABC. The ABC analysis tested for three scenarios (B1, B2, and B3) hypothesizing an introduction from one of the Asian countries. In this analysis, scenario B1 obtained the highest posterior probability ranging from 0.90 to 0.91 with a 95% CI of 0.81-0.99 and 0.88-0.94, which assumes an introduction from Korea. The ABC analysis revealed that one hypothetical scenario, which assumes an introduction of the soybean aphid into USA from Korea, was very robustly suggested than the other two scenarios (from China or Japan).