A method of assembling a wiring harness comprising a flat cable having a plurality of electric wires (14, 14a, 14b), and a connector attached to an end of the flat cable, said method comprising: assembling the flat cable by arranging the plurality of electric wires (14, 14a, 14b) having a specific length parallel to each other and weaving an elongated weft with respect to the plurality of electric wires (14, 14a, 14b) in a manner that the elongated weft is provided with crossing sections (15a, 15c) perpendicular to the plurality of electrical wires (14, 14a, 14b) and alternately rising and falling with respect to the plurality of electrical wires (14, 14a, 14b), and parallel sections (15b, 15d, 15e) continuous with the crossing sections and overlapping the electrical wires positioned at an edge of the plurality of electrical wires, wherein, as is illustrated in Figures 3 to 5 of the drawings, at ends of the plurality of electric wires (14, 14a, 14b), a first crossing section of the weft alternately rising and falling, and crossing with respect to the plurality of electric wires started from the electric wire disposed at the lowest end among the plurality of the electric wire is formed, a first parallel section overlapped with the electric wire disposed at the highest end is formed, a second crossing section alternately rising and falling, and crossing with respect to the plurality of electric wires started from the electric wire is formed, a second parallel section overlapped with the electric wire is formed and caught by the first crossing section, a third parallel portion again overlapped with the electric wire is formed, and, thereby, the crossing section alternately rising and falling from the electric wire and crossing to the electric wires is formed, and wherein the electrical wires (14, 14a, 14b) adjacent to each other are disposed with a gap therebetween, and the crossing sections (15a, 15c) adjacent to each other of the weft are disposed with a gap therebetween; moving the elongated weft away from an end of the flat cable, thereby separating the plurality of electric wires (14, 14a, 14b) from each other at the end of the flat cable; attaching female terminals to ends of the electric wires (14, 14a, 14b); and inserting the female terminals into terminal receiving chambers of a connector housing of the connector, thereby obtaining the wiring harness. assembling the flat cable by arranging the plurality of electric wires (14, 14a, 14b) having a specific length parallel to each other and weaving an elongated weft with respect to the plurality of electric wires (14, 14a, 14b) in a manner that the elongated weft is provided with crossing sections (15a, 15c) perpendicular to the plurality of electrical wires (14, 14a, 14b) and alternately rising and falling with respect to the plurality of electrical wires (14, 14a, 14b), and parallel sections (15b, 15d, 15e) continuous with the crossing sections and overlapping the electrical wires positioned at an edge of the plurality of electrical wires, wherein, as is illustrated in Figures 3 to 5 of the drawings, at ends of the plurality of electric wires (14, 14a, 14b), a first crossing section of the weft alternately rising and falling, and crossing with respect to the plurality of electric wires started from the electric wire disposed at the lowest end among the plurality of the electric wire is formed, a first parallel section overlapped with the electric wire disposed at the highest end is formed, a second crossing section alternately rising and falling, and crossing with respect to the plurality of electric wires started from the electric wire is formed, a second parallel section overlapped with the electric wire is formed and caught by the first crossing section, a third parallel portion again overlapped with the electric wire is formed, and, thereby, the crossing section alternately rising and falling from the electric wire and crossing to the electric wires is formed, and wherein the electrical wires (14, 14a, 14b) adjacent to each other are disposed with a gap therebetween, and the crossing sections (15a, 15c) adjacent to each other of the weft are disposed with a gap therebetween; moving the elongated weft away from an end of the flat cable, thereby separating the plurality of electric wires (14, 14a, 14b) from each other at the end of the flat cable; attaching female terminals to ends of the electric wires (14, 14a, 14b); and inserting the female terminals into terminal receiving chambers of a connector housing of the connector, thereby obtaining the wiring harness.