This paper proposes a novel method for creating Web services from functions or content provided by ordinary Web applications. Since service composition platforms for context-aware ubiquitous computing and communication services are being actively studied and developed, resources for composing a meaningful and useful service should be obtainable at all times and in any situation. Because such platforms use Web services as a uniform interface, the number of Web services that can be used as resources should be increased. Here, the use of wrappers that convert functions provided by ordinary Web applications into Web services is a very effective approach that can produce various kinds of services. To enable this mapping, our method extracts the HTML structure of a Web application by analyzing its features through fast Fourier transformation to produce an HTML spectrum. By converting the peak part of the HTML spectrum to the Web service interface, it can easily construct a Web service. This method will be useful for promoting ubiquitous business.