A disconnecting device comprising: a gas pressure tank; a support which is mounted at an inner circumference side of a tank front plate, by which a wall surface of the gas pressure tank is composed, and rotatably supports a three-phase operation hinge; an operation mechanism for disconnecting device, which is mounted at an outer circumference side of the tank front plate, and drives the three-phase link hinge; an insulating frame which is mounted at the inner circumference side of the tank front plate; a hinge terminal which rotatably supports one end portion of a movable blade which is linked to the three-phase operation hinge so as to be driven; and an connecting terminal which is separated by the other end portion of the movable blade; characterised in that the insulating frame includes at least a pair of side wall portions which are provided in a state where the side wall portions include a space portion between the mutual side wall portions and are separated at both sides; a first base portion which is integrally provided, between the pair of side wall portions, at one side end portion of the side wall portions, with the side wall portions, and includes a fixing portion by which the connecting terminal is fixed; second base portions which are integrally provided, between the pair of wall portions, with the side wall portions, and include a fixing portion by which the hinge terminal is fixed; and third base portions which are integrally provided, at the other side end portion of the side wall portions, with the side wall portions, and are fixed to the tank front plate; and the movable blade is rotatably provided at the second base portions in a front-back direction of the disconnecting device with respect to a vertical line in a state where a rotatable hinge of the hinge terminal is used as a supporting point, and the connecting terminal is provided at the first base portion which is arranged in an oblique upper direction with respect to a rotational supporting point of the movable blade; and the third base portions of the insulating frame include contacting surfaces for the tank front plate of the gas pressure tank; and the side wall portions are formed in a vertical plate shape in which a plate width direction is faced to a vertical direction in a state where the side wall portions are faced from the contacting surface for the tank front plate to a deep direction. a gas pressure tank; a support which is mounted at an inner circumference side of a tank front plate, by which a wall surface of the gas pressure tank is composed, and rotatably supports a three-phase operation hinge; an operation mechanism for disconnecting device, which is mounted at an outer circumference side of the tank front plate, and drives the three-phase link hinge; an insulating frame which is mounted at the inner circumference side of the tank front plate; a hinge terminal which rotatably supports one end portion of a movable blade which is linked to the three-phase operation hinge so as to be driven; and an connecting terminal which is separated by the other end portion of the movable blade; characterised in that the insulating frame includes at least a pair of side wall portions which are provided in a state where the side wall portions include a space portion between the mutual side wall portions and are separated at both sides; a first base portion which is integrally provided, between the pair of side wall portions, at one side end portion of the side wall portions, with the side wall portions, and includes a fixing portion by which the connecting terminal is fixed; second base portions which are integrally provided, between the pair of wall portions, with the side wall portions, and include a fixing portion by which the hinge terminal is fixed; and third base portions which are integrally provided, at the other side end portion of the side wall portions, with the side wall portions, and are fixed to the tank front plate; and the movable blade is rotatably provided at the second base portions in a front-back direction of the disconnecting device with respect to a vertical line in a state where a rotatable hinge of the hinge terminal is used as a supporting point, and the connecting terminal is provided at the first base portion which is arranged in an oblique upper direction with respect to a rotational supporting point of the movable blade; and the third base portions of the insulating frame include contacting surfaces for the tank front plate of the gas pressure tank; and the side wall portions are formed in a vertical plate shape in which a plate width direction is faced to a vertical direction in a state where the side wall portions are faced from the contacting surface for the tank front plate to a deep direction.