Solid Oxide Fuel Cell, which has high efficiency of electric power generation, is one of the key technologies for us to reach to the low carbon society. Over 30 years' basic research of SOFC leads it just to launch to practical use in the real world, whereas the accumulation of huge amount of research data, especially material data, urges to be restructured as well-organized knowledge to interoperably share and reuse for both enterprise and research institute. Therefore we establish such knowledge management infrastructure that enables designers to design SOFC system from the viewpoint of comprehensiveness; furthermore, we develop practical software tools to realize the infrastructure. Our approach mainly consists of three phases. The first phase is to build SOFC material database using MatML (Materials Markup Language) which is an XML (eXtensible Markup Language) designed for materials property data. The second phase is to externalize functional knowledge of devices as the form of function decompositions tree according to each process in product life cycle of SOFC by means of functional modeling technique based on ontology engineering. Finally those trees are integrated and visualized in 3D virtual space. We discuss a methodology of cross-process design support for SOFC systems, and introduce our prototype system based on the methodology.