Angiogenesis is regulated by the balance of pro-angiogenic factors and angiogenesis inhibitors, and the imbalance of these regulators is the cause of pathological angiogenesis, including tumor angiogenesis. Angiogenesis is required for tumor growth and metastasis, and thus constitutes an important target for the control of tumor progression. While the benefit of anti-angiogenic therapy is potentially profound, limitations have also been recognized by the results obtained thus far by clinical trials. Precise understanding of the process of angiogenesis should lead us to new regimens for more efficient anti-angiogenic therapy. This review focuses on our current understanding of the molecular mechanism of tumor angiogenic and the status of the anti-angiogenesis approach for cancer treatment.