Objectives: This study aimed to evaluate the effects of Cuscutae Semen water extract (CS) on MCF-7 human breast cancer cells. Methods: To clarify the results, we cultivated MCF-7 cells in cell culture plates. And then we extracted each of $100{mu}g/ml$, $300{mu}g/ml$, $600{mu}g/ml$ CS, gave it to MCF-7 cell. After these process we performed MTT assay to elucidate the ability of apoptosis. The result of mRNA was analyzed by RT-PCR. Results: Each of concentrated extracts CS decreased the survival rate of MCF-7 cells. CS decreased Bcl-2 which is known as a blocking cell apoptosis. Bax, caspase-3, P21 and RIP-1 that accelerate apoptogenic activity factors increased by CS. CS did not change the condition of caspase-8, caspase-9, P53 factors on MCF-7 cells. Furthermore caspase-8, caspase-9, P53 factors on MCF-7 cells does not make it more active but turn it on. Conclusions: According to the above results, we could suggest that CS can occur the apoptosis on MCF-7 cells.