Nano composite (NC) materials have a great potential to improve characteristics of electrical rotating machinery insulation systems. In order to understand the contribution of the NC materials on the insulation characteristics, a fundamental study which used semi-conductor field technologies is shown in this paper. The thin NC film is formed on a silicon substrate by a spin coating method. The silica particle dispersion in epoxy is analyzed by SEM. Furthermore, the insulation breakdown is measured and the nanoscale breakdown spots are investigated by STM. The results show that a NC which has a potential of actual application is developed and that the nanoscale method seems to be effective for evaluating NC materials.