To reduce the manufacturing cost of the housing of a bus duct by a method wherein bent parts which face the edge end parts in a direction parallel to a bus-duct line are installed at leat at an upper plate or a lower plate, and fitting parts are installed at the bent parts.

Bent parts 31 which face the edge end parts 30 of an upper part and a lower part in a direction parallel to a bus-duct line are installed at least at the upper plate 12 or the lower plate 14. Fitting parts 32 are installed at the bent parts 31. Accordingly, a line-part upper plate 12a and a line-part lower plate 14a can be fitted with the tough of a button to line-part side plates 13a which sandwich a bus bar. Since the fitting parts 32 are hooked by the bent parts 31 in the line-part side plates 13a, the line-part upper plate 12a and the line-part lower plate 14a can be fitted to the line-part side plates 13a. Therefore, in an assembling operation, the line-part upper plate, the line-part lower plate, a connection-part upper plate and a connection part lower plate can be attached without being tightened by bolts. As a result, the assembling time of this housing structure can be shortened, and the production cost of this bus duct can be reduced.