PURPOSE: A gas circuit breaker is provided to increase the amount of gas of an expansion room by compressing a compression room by using a roller and a compression room support. CONSTITUTION: A fixing unit includes a fixed arc contact(11) and a first fixing contactor(12). A movable arc contact point selectively contacts the fixed arc contact. A cylinder accommodates the movable arc contact point. The fixing unit includes a second fixed contact(21) guiding the movement of the cylinder. The piston is arranged inside the second fixed contact.
