A circuit interrupter comprising: a fixed terminal including a fixed contact; a movable contactor including a movable contact connected to the fixed contact; a moving mechanism (520, 53) configured to move the movable contactor from a closed position where the movable contact is connected to the fixed contact to an open position where the movable contact is separated from the fixed contact; a squib configured to generate gas by combustion; a case accommodating the squib and having a sleeve; and accommodation for accommodating the fixed contact and the movable contactor; the moving mechanism (520, 53) including: a pressurized chamber for receiving pressure of the gas; and a piston for receiving pressure inside the pressurized chamber and moving the movable contactor into the open position by applying a force to the movable contactor in a direction toward the open position; characterized in that the case further has two channels interconnecting the inside and the outside of the case formed in a side wall of the sleeve of the case; each channel is configured to be formed in part of the side wall of the sleeve and to connect the pressurized chamber and the accommodation; and when the movable contactor is in the open position, part of the gas is introduced into the accommodation from the pressurized chamber via the channels. a fixed terminal including a fixed contact; a movable contactor including a movable contact connected to the fixed contact; a moving mechanism (520, 53) configured to move the movable contactor from a closed position where the movable contact is connected to the fixed contact to an open position where the movable contact is separated from the fixed contact; a squib configured to generate gas by combustion; a case accommodating the squib and having a sleeve; and accommodation for accommodating the fixed contact and the movable contactor; the moving mechanism (520, 53) including: a pressurized chamber for receiving pressure of the gas; and a piston for receiving pressure inside the pressurized chamber and moving the movable contactor into the open position by applying a force to the movable contactor in a direction toward the open position; characterized in that the case further has two channels interconnecting the inside and the outside of the case formed in a side wall of the sleeve of the case; each channel is configured to be formed in part of the side wall of the sleeve and to connect the pressurized chamber and the accommodation; and when the movable contactor is in the open position, part of the gas is introduced into the accommodation from the pressurized chamber via the channels. a pressurized chamber for receiving pressure of the gas; and a piston for receiving pressure inside the pressurized chamber and moving the movable contactor into the open position by applying a force to the movable contactor in a direction toward the open position; characterized in that the case further has two channels interconnecting the inside and the outside of the case formed in a side wall of the sleeve of the case; each channel is configured to be formed in part of the side wall of the sleeve and to connect the pressurized chamber and the accommodation; and when the movable contactor is in the open position, part of the gas is introduced into the accommodation from the pressurized chamber via the channels.