The invention relates to a gas circuit breaker which can protect a coupling member and improve cutting performance for high-temperature and high-pressure gas caused by electric arcs generated when short-circuit current is cut off. In order to solve the above-described problems, a gas circuit breaker of the present invention has an insulating nozzle disposed so as to cover an inner surface of a coupling member (40) such that an end surface (40a) of the coupling member (40) and an end surface (4a) of the insulating nozzle (4) form one surface (the end surface (40a) of the coupling member (40) is flush with the end surface (4a) of the insulating nozzle (4)), in order to suppress contact between a high-temperature and high-pressure gas (50) generated by an arc and the coupling member (40) coupling the insulating nozzle (4) and a driving rod (41).