Provided is a power supply structure for a sliding door, said structure making it possible to minimise the manufacturing cost and reduce the size and weight. The present invention comprises an other end holding part (3) that holds the other end of an electrical wire (W) disposed between a door panel (P) and a door trim (T). The other end holding part (3) is constituted by providing: a base (31) to which the door panel (P) or the door trim (T) is fixed; a rotating arm (32) that is supported rotatably by the base (31) and holds the electrical wire at the tip of the arm (32); and an impelling means that impels the rotating arm (32) in the direction in which extra length of electrical wire (W) is taken up. An electrical wire guiding part (12) is formed at the lower edge (11) of the door trim (T), said guiding part (12) having a first folded part (12A) that is folded towards the outside of the vehicle, and a second folded part (12B) that is folded downward and towards the inside of the vehicle from the tip of the first folded part (12A).