Electrical properties of ethylene propylene rubber (EPR) were studied in the cryogenic temperature region to examine the possibility of its application to the solid electrical insulating material of superconducting power apparatuses and cables. Dissipation factor of EPR sheet under high electric field is rather large even at cryogenic temperatures. Electric strength of EPR film is a little superior to that of PE at liquid helium temperature. The use of EPR as a solid electrical insulation at cryogenic temperatures is discussed based on the results obtained. Furthermore, extruded EPR insulated cable was fabricated as an example of EPR solid insulation. The cable showed fine mechanical and electrical performance in the cryogenic temperature region. EPR is suitable for electrical insulating material of superconducting power apparatuses and cables.