The present invention relates to a pharmaceutical composition for inhibiting growth of cancer stem cells, containing an aldehyde inhibitor and a biguanide-based compound. The pharmaceutical composition according to the present invention contains a combination of an aldehyde inhibitor and a biguanide-based compound, which can effectively inhibit the growth of cancer stem cells such as neurospheres and can also inhibit the proliferation, invasion and metastasis of cancer cells, thereby preventing and/or treating cancer such as brain cancer.
