To provide a support insulator whose weight is reduced and which is lightweight and is excellent in mechanical strength by forming a covering layer composed of silicone rubber in an outer peripheral part of a hollow truncated cone-shaped core material having a shade-like recessed and projecting part, composed of a highly rigid insulating member, arranging a terminal metal fitting in an upper end part of the core material, and constituting so as to adhere/fix a flange metal fitting to a lower end part of the core material.

A resin support insulator 1 has a hollow truncated cone-shaped core material 2, having a shade-like recessed and projecting part composed of a highly rigid insulating member, for example, an ABS resin, and forms a covering layer 6 having a shade-like recessed and projecting shape composed of silicone rubber formed in an outer peripheral part of its core material 2 through an adhesive primer layer. A terminal metal fitting 7 to connect/fix an electric power impressing conductor part is adhered/fixed to an upper end part of the core material 2, and a flange metal fitting 5 installed on the apparatus casing side is adhered/fixed to a lower end part of the core material 2, respectively. Afterwards, liquid silicone rubber 9 is applied/ hardened on an inside surface of the core material 2, and the inside surface of the core material 2 is smoothed.