Three different water-based traps with living adults of female, male and without adults were installed in a soybean field to examine the attractiveness of the bean bug, Riptortus clavatus. In the female-baited trap, most adults caught were male whereas female adults were rarely caught. However, the number of adults attracted in the malebaited trap was the same in the sex ratio. Meanwhile adults of female and male were rarely captured by the non-adults trap. The results, therefore, indicated that the female adult of R. clavatus has a sex attractant.