By processing triangle or square pyramid shaped indents on a flat sheet, panels with periodical indents in regular plane tiling patterns are formed. Highly rigid core panels are newly developed by setting this panel (as top panel) on a reversed one (as bottom panel), and gluing/welding them at the apexes of pyramids to the vertexes of the tiling patterns in the bottom panel. The basic model named Dia-Core is a panel created in the form of Octet-Truss developed by Fuller which corresponds to the space filling model consisting of a combination of two tetrahedra and one octahedron. By varying the geometric patterns that appear on the panel surfaces, various modified models with larger welding portions are created systematically. And some samples were manufactured using thin metal sheets. Finally, by using FEM modal analysis and excitation test, basic vibration characteristics of dia-core are investigated.