A dead tank vacuum circuit breaker of the invention has an object to obtain a dead tank vacuum circuit breaker in which an immovable end of a vacuum valve is supported on a tank immovable side via an insulating support member and a support frame or the immovable end of the vacuum valve is supported on a tank movable side via an insulating support rod, so that an insulating support member supporting a movable end of the vacuum valve is omitted, while an opening portion is provided to the movable side of the tank and a bushing center conductor has a slidable connection portion that is axially expandable and contractible, so that a de-assembly range can be minimized when the vacuum valve is replaced.