A wire branch structure (1) includes a plurality of wires (3) and a shield member (5) which covers the circumference of the wires (3). One end side of each of the wires (3) is inserted in a main line side shell (7). The other end side of each of the wires (3) is branched from the main line side shell (7) and is inserted into branch line side shells (9, 11) respectively. An isolation part (15) is provided in the shield member (5), which isolates the wires (3) adjacent to a branch part (13) in which the other end side of each of the wires (3) is inserted in the branch line side shells (9, 11) respectively and branched.