1. A mesh model creating method comprising: a mesh forming step dividing a region that is a target of a simulation into a plurality of polygonal meshes so that each node within the region is positioned within one mesh and a boundary line between two mutually adjacent meshes is formed by a perpendicular bisector with respect to a straight line that connects the nodes within the two mutually adjacent meshes, and storing data of each of the meshes in a memory part; a first computing step computing an inductance value and a resistance value of an interval between the two mutually adjacent meshes based on the data of the meshes stored in the memory part, using predetermined computation formulas prestored in the memory part, and storing the computed inductance value and resistance value in the memory part; and a mesh model creating step creating a mesh model based on the data of the meshes and the computed inductance value and resistance value that are stored in the memory part.