A method of storing substantial data integrating shape and physical properties comprising (A) inputting external data 12 consisting of boundary data of an object 1, (B) dividing, by modified Octree division, the external data into cubical cells 13 which boundary surfaces are orthogonal to each other, and (C) storing the values of various physical properties for each of the cells. Furthermore, in step (B), each of the divided cells 13 is classified to non-boundary cells 13a located in the interior of the object or in a region outside of the object, and boundary cells 13b including boundary surfaces. Thereby, substantial data integrating shape and physical properties can be stored in small storage capacity, thus enabling the integration of CAD and simulation.