The present invention relates to a composition which is for preventing or treating breast cancer and includes salidroside and betulin as active ingredients. The composition according to the present invention including a mixture in which salidroside and betulin are mixed in a mass ratio of 2:1 or 1:2 exhibits an effect of treating or preventing breast cancer by inhibiting the cell proliferation of MCF-7, which is a human-derived breast cancer cell line. Thus, the composition is expected to be usefully used as a pharmaceutical composition for preventing or treating breast cancer using a mixture of salidroside and betulin, and as a functional food composition for alleviating or preventing breast cancer.
