A gas circuit breaker includes a breaking unit tank incorporating a fixed electrode and a movable electrode, a spring operation device including a breaking spring and a closing spring and configured to move the movable electrode, and a mechanism unit configured to couple the movable electrode side and the spring operation device side and transmit power received from the spring operation device to the movable electrode. The spring operation device is supported by a frame. The frame is fixed to a rear plate provided in a mechanism unit frame of the mechanism unit. A breaking spring case and a closing spring case of the spring operation device are fixed to pedestals via a plate member 38 and a support section 7.