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 (H2) 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 (H2) 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 (H2) 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 (H2) 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 (H2) 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 (H2) 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 . <EOS>