<,正,>, In an attempt to prepare a polymeric solid electrolyte with both high ionic conductivity at ambient temperature and adequate mechanical strength, an ionic conducting IPN composed of bisphenol A epoxy resin/polyethylene glycol containing LiClO,4, was synthesized. The dependence of conductivity was investigated as a function of salt content, composition and temperature. It has been revealed that a maximum of conductivity appeared when EO/Li=25, where EO denotes the—（CH,2,CH,2,O）-unit in polyethylene glycol, and that the temperature dependence of conductivity followed VTF equation, suggesting that the motion of ionic carriers resulted from the segmental motion of the polymer. When glycerol epoxy resin was used instead of bisphenol A epoxy, the ambient temperature （25℃） conductivity could somewhat further be raised up to 3×10,-5, S/cm.