A gas-insulated circuit breaker comprising: a fixed contact having a hollow formed therein; a fixed arc contact disposed in the hollow of the fixed contact; a fixed-side conductor provided to surround the fixed contact and configuring a gap between the fixed-side conductor and the fixed contact as a discharge path for an insulation gas; a movable contact having a hollow formed therein; a movable arc contact disposed in the hollow of the movable contact; a movable-side conductor provided to surround the movable contact and configuring a gap between the movable-side conductor and the movable contact as a discharge path for an insulation gas; a first extension part formed on the fixed-side conductor and extending at least a portion of the discharge path for the insulation gas of the fixed-side conductor to decrease a degree of pressure of the insulation gas flowing into the discharge path of the fixed-side conductor; and a second extension part formed on the movable-side conductor and extending at least a portion of the discharge path for the insulation gas of the movable-side conductor to decrease a degree of pressure of the insulation gas flowing into the discharge path of the movable-side conductor; and wherein the fixed-side conductor has a cylindrical shape in which at least one first extension part is formed on a side of the fixed-side conductor, and the movable-side conductor has a cylindrical shape in which at least one second extension part is formed on a side of the movable-side conductor, characterized in that the first extension part is formed as an outwardly bent portion of a body of the fixed-side conductor and the second extension part is formed as an outwardly bent portion of a body of the movable-side conductor. a fixed contact having a hollow formed therein; a fixed arc contact disposed in the hollow of the fixed contact; a fixed-side conductor provided to surround the fixed contact and configuring a gap between the fixed-side conductor and the fixed contact as a discharge path for an insulation gas; a movable contact having a hollow formed therein; a movable arc contact disposed in the hollow of the movable contact; a movable-side conductor provided to surround the movable contact and configuring a gap between the movable-side conductor and the movable contact as a discharge path for an insulation gas; a first extension part formed on the fixed-side conductor and extending at least a portion of the discharge path for the insulation gas of the fixed-side conductor to decrease a degree of pressure of the insulation gas flowing into the discharge path of the fixed-side conductor; and a second extension part formed on the movable-side conductor and extending at least a portion of the discharge path for the insulation gas of the movable-side conductor to decrease a degree of pressure of the insulation gas flowing into the discharge path of the movable-side conductor; and wherein the fixed-side conductor has a cylindrical shape in which at least one first extension part is formed on a side of the fixed-side conductor, and the movable-side conductor has a cylindrical shape in which at least one second extension part is formed on a side of the movable-side conductor, characterized in that the first extension part is formed as an outwardly bent portion of a body of the fixed-side conductor and the second extension part is formed as an outwardly bent portion of a body of the movable-side conductor.