The present invention relates to a composition for inhibiting growth of cancer stem cells, which includes an EXT1, LDHB, CD109, EFEMP2, RASIP1 or SERPINE1 gene expression inhibitor as an active ingredient, and a method of treating cancer using the same. The composition has targeted therapeutic activities against cancer stem cells important for resistance, metastasis and recurrence of breast cancer, and thus can be useful in fundamentally treating, preventing or alleviating cancer such as breast cancer by directly inhibiting expression of EXT1, LDHB, CD109, EFEMP2, RASIP1 or SERPINE1 which are very important for growth of the cancer stem cells.
