This article intends to probe the meaning of Taiwan's democratization for Taiwan's security-whether democratization increases Taiwan's security or adversely creates more uncertainty. It is argued in this article that three important changes in Taiwan's external relations and security environment have arisen from the process of democratization. First, Taiwan's democratization has made domestic politics the critical factor in the decision-making of the island's foreign policy and security policy. Second, Taiwan's democratization has caused alternations in Taiwan's arching security environment; Beijing and Washington, especially, have correspondingly changed their attitudes toward cross-strait policy and Taiwan's security respectively. Third, different Taiwanese identities accompanying Taiwan's democratization are challenging the constraints set by present cross-strait relations and the international diplomatic structure.