A gas circuit breaker (201;301;401;501) comprising: a sealed container filled with an arc-extinguishing gas; a first contact part and a second contact part (20;320) provided to come into contact with each other in a closed electrode state and to be separated from each other in the sealed container in a predetermined direction in an open electrode state, wherein the second contact part (20;320) comprises a conduction contact (21;321;421) formed in a tubular shape extending in the predetermined direction and configured to come into contact with the first contact part in the closed electrode state; an operation mechanism connected to the first contact part and configured to separate the first contact part and the second contact part (20;320) from the closed electrode state to the open electrode state; an insulating nozzle formed in a tubular shape and configured to surround arc discharge generated between the first contact part and the second contact part (20;320) in the open electrode state while being displaced in conjunction with the first contact part in a separation process of the first contact part and the second contact part (20; 320); a pressure accumulator configured to cause accumulation in pressure of the arc-extinguishing gas in a compressive manner by variably changing a capacity of a puffer chamber in conjunction with the separation process of the first contact part and the second contact part (20;320) and to discharge the arc-extinguishing gas to a flow path in the insulating nozzle to perform blasting with respect to the arc discharge while accumulating the pressure of the arc-extinguishing gas; and an electric field shield (280;380;580) attached to the insulating nozzle, wherein the electric field shield (280;380;580) is configured so as to come into contact with the conduction contact (21;321;421) of the second contact part (20;320) in the completely open electrode state such that the electric field shield (280;380;580) has the same potential as the conduction contact (21;321;421), and so as to not come into contact with the conduction contact (21;321;421) of the second contact part (20;320) from a time when the first contact part and the second contact (20;320) part are separated from each other in the separation process, thus having a floating potential in a period of at least part of the separation process. a sealed container filled with an arc-extinguishing gas; a first contact part and a second contact part (20;320) provided to come into contact with each other in a closed electrode state and to be separated from each other in the sealed container in a predetermined direction in an open electrode state, wherein the second contact part (20;320) comprises a conduction contact (21;321;421) formed in a tubular shape extending in the predetermined direction and configured to come into contact with the first contact part in the closed electrode state; an operation mechanism connected to the first contact part and configured to separate the first contact part and the second contact part (20;320) from the closed electrode state to the open electrode state; an insulating nozzle formed in a tubular shape and configured to surround arc discharge generated between the first contact part and the second contact part (20;320) in the open electrode state while being displaced in conjunction with the first contact part in a separation process of the first contact part and the second contact part (20; 320); a pressure accumulator configured to cause accumulation in pressure of the arc-extinguishing gas in a compressive manner by variably changing a capacity of a puffer chamber in conjunction with the separation process of the first contact part and the second contact part (20;320) and to discharge the arc-extinguishing gas to a flow path in the insulating nozzle to perform blasting with respect to the arc discharge while accumulating the pressure of the arc-extinguishing gas; and an electric field shield (280;380;580) attached to the insulating nozzle, wherein the electric field shield (280;380;580) is configured so as to come into contact with the conduction contact (21;321;421) of the second contact part (20;320) in the completely open electrode state such that the electric field shield (280;380;580) has the same potential as the conduction contact (21;321;421), and so as to not come into contact with the conduction contact (21;321;421) of the second contact part (20;320) from a time when the first contact part and the second contact (20;320) part are separated from each other in the separation process, thus having a floating potential in a period of at least part of the separation process.