A flat cable includes an enclosure sleeve that encloses a selected section of a cluster section of a flexible substrate. The enclosure sleeve has opposite ends respectively coupled to a first water resistant member and a second water resistant member. Each water resistant member includes a base forming a hollow channel and an insertion end extending from the base. The insertion end is fit to an inside or outside wall of an end of the enclosure sleeve. The first water resistant member, the second water resistant member, and the enclosure sleeve are combined together to form a water resistant section. When the flexible substrate is subjected to a stretching force in an extension direction or a torque applied in a rotation direction, the flexible substrate is allowed to undergo relative displacement with respect to the first water resistant member, the second water resistant member, and the enclosure sleeve.