A gas insulated electrical apparatus, comprising: - a container filled with insulating gas; - a high voltage conductor arranged inside the container and applied with a prescribed voltage; and - an insulating support member configured to insulate and support the high voltage conductor relative to the container, the high voltage conductor being covered by a first dielectric film, the first dielectric film having a first main surface exposed inside the container, and a second main surface located on a side opposite to the first main surface and being in contact with the high voltage conductor, the first dielectric film being provided with a first through hole extending from the first main surface to the second main surface, characterized in that the first through hole has an inner circumferential surface on which a first coating film is formed, such that a hole diameter of the first through hole is less than a diameter of an electron avalanche in a state where the gas insulated electrical apparatus is used, wherein the hole diameter of the first through hole is the distance between opposed planes of said first coating film, formed on the inner circumferential surface, and facing each other, with an internal space interposed therebetween, and a thickness of the first coating film is thinner than a thickness of the first dielectric film. - a container filled with insulating gas; - a high voltage conductor arranged inside the container and applied with a prescribed voltage; and - an insulating support member configured to insulate and support the high voltage conductor relative to the container, the high voltage conductor being covered by a first dielectric film, the first dielectric film having a first main surface exposed inside the container, and a second main surface located on a side opposite to the first main surface and being in contact with the high voltage conductor, the first dielectric film being provided with a first through hole extending from the first main surface to the second main surface, characterized in that the first through hole has an inner circumferential surface on which a first coating film is formed, such that a hole diameter of the first through hole is less than a diameter of an electron avalanche in a state where the gas insulated electrical apparatus is used, wherein the hole diameter of the first through hole is the distance between opposed planes of said first coating film, formed on the inner circumferential surface, and facing each other, with an internal space interposed therebetween, and a thickness of the first coating film is thinner than a thickness of the first dielectric film. the high voltage conductor being covered by a first dielectric film, the first dielectric film having a first main surface exposed inside the container, and a second main surface located on a side opposite to the first main surface and being in contact with the high voltage conductor, the first dielectric film being provided with a first through hole extending from the first main surface to the second main surface, characterized in that the first through hole has an inner circumferential surface on which a first coating film is formed, such that a hole diameter of the first through hole is less than a diameter of an electron avalanche in a state where the gas insulated electrical apparatus is used, wherein the hole diameter of the first through hole is the distance between opposed planes of said first coating film, formed on the inner circumferential surface, and facing each other, with an internal space interposed therebetween, and a thickness of the first coating film is thinner than a thickness of the first dielectric film.