In the present invention, provided are a treatment of breast cancer stem cells via the inhibition of nanog and the activity of ERK and a method for screening breast cancer using the same. In the present invention, a composition for treating breast cancer stem cells comprises an inhibitor for inhibiting nanog as an active ingredient wherein the nanog inhibitor consists of siRNA or nanog mutant plasmid. In the present invention, the nanog has various effects of controlling the formation of tumor from KUCSLCs and plays a key role in controlling KUCSLCs reaction for self-regeneration and drug resistance.COPYRIGHT KIPO 2015본 발명은 나노그 억제와 이알케이 활성화를 통한 유방암 줄기세포 치료 및 스크리닝 방법에 관한 것이다.