National Secure Data Service Act This bill establishes a National Secure Data Service demonstration project. The bill follows a recommendation in the 2017 Commission on Evidence-Based Policymaking report calling for establishment of such a service to facilitate access to data across government. The project shall be (1) aligned with the principles, best practices, and priority actions recommended by the Advisory Committee on Data for Evidence Building; and (2) managed by the National Center for Science and Engineering Statistics. The project shall engage with state and federal agencies to collect, acquire, analyze, report, and disseminate statistical data in the United States and other nations to support government-wide evidence-building activities. The bill includes provisions to ensure confidentiality and transparency.