Electron beam irradiated fluorinated materials, which are used for an OSR (Optical Solar Reflector) of spacecraft have been investigated using a space charge measurement system under DC high stress. It was found that a large amount of space charge accumulated in the electron beam irradiated ethylene-tetrafluoroethylene (ETFE) and fluorinated ethylene-propylene copolymer (FEP) under DC high stress, while it was not observed in non-irradiated them. In this report, a dependence of relaxation time after the irradiation on the space charge accumulation characteristics was also studied.