SLIDING DOOR OPENING/CLOSING STRUCTURE

PROBLEM TO BE SOLVED: To provide a sliding door opening/closing structure which reduces a size of a slide rail for guiding a roller unit, and reinforces a body panel of a vehicle body.SOLUTION: A roller unit 20 arranged on a sliding door 13 includes: a vertical roller 21 and a horizontal roller 22 which rotate along a slide rail 30; and a roller bracket 23 which rotatably supports the vertical roller 21 and horizontal roller 22 and is mounted on the sliding door 13. The slide rail 30 for guiding the roller unit 20 includes: a rail bottom surface 31 on which the vertical roller 21 rolls and which is fixed on the body panel 18; a rail upper surface 32 which covers above the horizontal roller 22 and is fixed on the body panel 18; an outer side vertical wall 33 which is extended from the rail upper surface 32 downward and restricts movement of the horizontal roll 22 to an outer side of a vehicle width direction; and a connecting wall 34 which connects the rail bottom surface 31 and the rail upper surface 32 in an inner side position in the vehicle width direction from the outer side vertical wall 33.