PURPOSE: To facilitate manufacturing of outer box by employing a cabinet type bushing pocket, to be provided on outside of an outer box, and installing it so that it becomes perpendicularly to length-wise direction of the outer box.

CONSTITUTION: A bushing pocket 13, to be provided so that it stickes out from a cover 3 of an outer box 2, is made into a cabinet type for attaching of a high-pressure bushing and a low-pressure bushing 11, 12 at the same time, arranged so that it becomes perpendicular to the outer box's length-wise direction, and both ends of the bushing pocket are extended to both ends of the outer box. By using, in this manner, a common cabinet type bushing pocket for high-pressure bushing and a low-pressure bushing, employing a common connecting hand hole 14 and supporting it by all phases of UVW, it is possible to simplify the structure. And also, as the pocket 13 serves the purpose of reinforcement of the cover 3, a separate reforcing material is not required, manufacturing of the outer box 2 can be simplified, a lead wire 4 can be shortened and use of a supporting insulator can be eliminated.