Various kinds of access control mechanisms have been employed in today's computer systems to protect confidential information. Since high expertise is required for the system configuration maintenance, detecting vulnerabilities due to configuration errors is a difficult task. In this paper, we propose a model-based configuration verification method that can find complex errors of two major access control mechanisms, network packet filtering and file access control. This method constructs an information flow model using the configurations of the two mechanisms and verifies whether the system is configured to suffice access policies defined by system administrators. Through the development of a prototype system and its experimental use, we confirmed that the proposed method could discover configuration errors of Web servers that might cause information leakage.