A pressure tank which seals and contains an electrical device, is formed with an opening portion corresponding to a terminal portion provided on the electrical device. A porcelain tube which is disposed so as to protrude with respect to the pressure tank, is fixed to the opening portion at a base portion thereof, and is provided with a terminal conductor at a leading end portion thereof. A first connection conductor is led out into a center portion of the porcelain tube at one end thereof, and is connected to the terminal conductor at the other end thereof. A second connection conductor which has a concave section to be fitted onto the first connection conductor at one side thereof, is connected to the terminal portion at the other side thereof. A contact is disposed between the first connection conductor and the concave section of the second connection conductor.