<p>The present invention provides an insulating spacer (16) for a high-voltage conductor (6) constructed with a plastic made of an epoxy resin composition so that the volumetric specific resistance of a shield electrode (12, 13) increases toward the median point between a container (2) and the conductor (6) and a method for manufacturing the shield electrode (12, 13) used therein. The insulating spacer (16) according to the present invention can lessen the concentration of electric fields in the boundary areas between the shield electrode (12, 13) and the insulating member (11) with the result that reliability is improved and service life is lengthened. <IMAGE></p>