A power supply structure for a sliding door includes other end-side holding portion which holds the other end of the electric wire. The other end-side holding portion includes first and second turning arms which are rotatably supported directly or indirectly by the sliding door and hold the electric wire at a tip end thereof, and biasing unit which biases the first turning arm in a direction to absorb an extra length of the electric wire. The tip end of the second turning arm inclines with respect to a longitudinal direction of a vehicle at climbing-over timing at which the electric wire climbs over a predetermined climbing-over position of a lower end edge of a door trim which configures the sliding door on an inner side of the vehicle when the sliding door is slid and moved.