To allow a cable guide for reducing load to descend when a downward load is exerted from above during opening of a sliding door by sheathing a wire harness with the cable guide having a small degree of freedom in the vertical direction.

The wire harness suspended between support devices disposed in the sliding door and a vehicle body is sheathed with the caterpillar shaped cable guide in which link members are sequentially coupled to each other. A support frame fixed to the sliding door or/and the vehicle body is disposed in at least one of the support devices of the sliding door and the vehicle body. A slider being energized upward is hung on the support frame through an elastic member, and the wire harness is passed through a through-hole disposed in the slider. The distal end side of the cable guide sheathing over the wire harness is attached to the slider. When the load is exerted from above on the cable guide sheathing over the wire harness, the elastic member is stretched to allow the cable guide to descend. The cable guide automatically ascends when the load is released.