A vacuum circuit breaker includes a tank containing an electrical device. An opening corresponds to a terminal of the electrical device. A porcelain tube protruding from the tank is fixed to an opening base, and has a terminal conductor. A first connection conductor in the porcelain tube is connected to the terminal conductor. A second connection conductor is arranged in the porcelain tube. A third connection conductor is arranged between the first and the second connection conductor, has a closed end concave section fitted onto the first connection conductor and is connected to the second connection conductor by a fastener. A contact is disposed between said first connection conductor and the third connection conductor. The third and second connection conductors are made of a solid conductor. A center of the third connection conductor and a center of the second connection conductor are formed with a threaded section.