The advent of emerging technologies such as Web services, service-oriented architecture, and cloud computing has enabled us to perform business services more efficiently and effectively. However, we still suffer from unintended security leakages by unauthorized services while providing more convenient services to Internet users through such a cutting-edge technological growth. Furthermore, designing and managing Web access control policies are often error-prone due to the lack of logical and formal foundation. In this paper, we attempt to introduce a logic-based policy management approach for Web access control policies especially focusing on XACML (eXtensible Access Control Markup Language) policies, which have become the de facto standard for specifying and enforcing access control policies for various applications and services in currentWeb-based computing technologies. Our approach adopts Answer Set Programming (ASP) to formulate XACML that allows us to leverage the features of ASP solvers in performing various logical reasoning and analysis tasks such as policy verification, comparison and querying. In addition, we propose a policy analysis method that helps identify policy violations in XACML policies accommodating the notion of constraints in role-based access control (RBAC). We also discuss a proof-of-concept implementation of our method called XACML2ASP with the evaluation of several XACML policies from real-world software systems.