The amniotic membrane secretes various substances and has many functions, such as antiangiogenic activity, immunoregulatory activity, pro-apoptotic activity, antimicrobial properties, antifibroblastic activity, cell migration, and cell growth-promoting activity. Of these functions, we mainly focus on antiangiogenic activity, immunoregulatory activity, and pro-apoptotic activity and their applications in tumor biology. The amniotic membrane provides a privileged space anatomically, physiologically, and immunologically to the fetus. Angiogenesis occurs in tumor growth, and destruction of the immunologic barrier is an inevitable process in tumor invasion and metastasis. Regarding tumor cell killing, the pro-apoptotic pathway should be activated. Therefore, if we could apply the characteristics of the amniotic membrane to tumor biology, we might encounter a breakthrough in cancer treatment. For example, if a tumor mass could be enclosed by the amniotic membrane surgically, the growth of the tumor might be retarded. Further experiments and clinical trials should be conducted to verify our hypotheses.