1. An apparatus for creating a mashup web application, comprising: one or more storage devices storing code configured to implement: a web application authoring unit configured to generate a web application initial page from previously stored block resources and web application resources, during web application authoring login, receive UI-based web application authoring information through the web application initial page, and generate web application metadata; a block authoring unit configured to generate the block resources provided to the generation of the web application initial page, at least in part by searching for an open API in response to a request; and a workflow management unit configured to generate a final web application by verifying a workflow of the web application metadata.