A gas-insulated switchgear apparatus includes a center conductor 2, a current transformer 4 surrounding the center conductor 2, an electric field shield 5, and a metallic vessel 1. The electric field shield 5 is located between the center conductor 2 and the current transformer 4 and surrounds the center conductor 2. The current transformer 4 and the electric field shield 5 constitute a tubular part that outputs a signal representing an electric physical quantity. The metallic vessel 1 is filled with an insulating gas 19. The tubular part has an opening 6 formed therein. In a posture in which the center axis of the tubular part about which the tubular part surrounds the center conductor 2 is substantially horizontal, the opening 6 is located in a surface of the tubular part, which surface is included in a lower portion of the tubular part and faces the center conductor 2.