The microwave excited surface wave plasma process enables us to do less damage processing by active neutral gaseous and wide area processing. On the other hand, the surface wave plasma is strong coupling phenomena of microwave and plasma, and detail understanding of the phenomena by any pure analytical methods is not easy. Authors have been working in development of numerical simulation tool for this equipment by using FDTD method. So far the FDTD method with appropriate plasma macro model which is partially based on experimental data of electron density was proposed and good agreements with experimental results was obtained. As the next stage of the development of the numerical code, this paper presents estimation of electron density distribution in simulation.