Friction Stir Welding (FSW) for aviation and automobile applications has been investigated at Osaka East Urban Area Industry-Government-Academia Collaboration Project on FSW sponsored by a Japanese ministry of education, culture, sports, science and technology, 2004-2007. The objective of this project is the three dimensional (3D) FSW of light metallic materials. The project consists of two simultaneous investigations. One is the approach from material side. The establishment of optimum FSW conditions and the construction of the FSW equation between weld condition and formed microstructure. The other is the approach from 3D software. The construction of optimum algorism for 3D FSW is the main theme. The construction of 3D FSW expert system for aluminum alloys, magnesium alloys and titanium alloys is the goal of us in combination of the results developed by the two research group.