In this paper, a generic Computer Aided Software Engineering (CASE) tool builder - MetaBuilder is proposed and described in detail. It is a graph-driven tool, not only for CASE application projects but for new methodology and new CASE tool design. MetaBuilder provides the following functionality: a rapid CASE tool developing environment for users to create new or modify old methodologies in graph manipulations; an integration platform for users to plug their own programs into MetaBuilder to realize their own special functionality; a central repository and a set of Graphic User Interface (GUI) classes for resource reuse that can greatly lighten users' developing work, shorten users' learning and developing time; and finally, a hierarchical design mechanism and a flexible type definition method based on nested graph structures for large and complex CASE methodology and application project design. All generated tools are integrated due to our unique data model. The implementation of MetaBuilder is also presented in this paper.