It is concerned that the recent expansion of the application environment of power electronics to high-altitude and/or high-radiation environments will cause deteriorations of insulation materials used in power electronics due to charging caused by cosmic ray irradiation. With respect to the high-radiation environments, the exposure of high-energy charged particles such as protons, electrons, etc. to the insulation materials gives rise to the charge accumulations, which dielectric BD (breakdown) of the materials and make the power electronics equipment inoperable, in the materials due to changes in the insulation characteristics of the materials. Therefore, in this paper, we report the feasibility study on the deteriorations of BD characteristics of three insulation materials (Alicyclic EP, OCN, PPS) due to proton or electron irradiation. As a result, it was found that BDE (BD electric field) of some insulation materials (Alicyclic EP, OCN) decreases due to proton or electron irradiation. The oxidation and the change in the electric field distribution in the materials caused by proton or electron irradiation may be one of the reasons for the decreases in BDE of the materials.