To cover a wire not to be exposed at a branch position in a wire harness where a main line and a branch line are sheathed with corrugated tubes.

A corrugated tube for sheathing the main line of a wire harness is cut at a branch, the corrugated tubes thus cut on the opposite sides are partially removed in the circumferential direction in a region of a required length from the cut end to form arcuate parts each of which partially opens, and according to the direction and the size of a line branched from the main line, the opening angle is adjusted in the circumferential direction by overlapping the arcuate parts of the corrugated tubes on the opposite sides within a required angular range, the opening length is adjusted by overlapping the arcuate parts on the opposite sides within a required length range, and then the overlapped crests and roots on the inside and outside of the arcuate part are fitted each other.