A highly heat-resistant fluororesin, such as tetrafluoroethylene resin or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, is filled with 0.5 to 1 weight % of a non-black insulating pigment that has a heat resistance such that discoloration does not occur when the fluororesin is baked. Green insulating pigment whose main component is a TiO2—CoO—NiO—ZnO system or a ZnO—CoO system, or blue insulating pigment whose main component is a CoO—Al2O3 system or a CoO—Al2O3—Cr2O3 system is used singly or in a combination, as the non-black insulating pigment. A highly arc-resistant insulator is provided that secures an insulating capacity and at the same time that secures an excellent ability to prevent both interior and exterior deterioration of the insulator and that avoids color heterogeneity and localized discoloration.