SUPPORT STRUCTURE OF SIDEWAY OPEN TYPE BACK DOOR

PROBLEM TO BE SOLVED: To provide the support structure of a sideway open type back door which can increase the strength of not only a back door hinge installation part but also its intermediate part and prevent the deformation of a rear pillar. SOLUTION: An extension panel 12 is bridged and joined between an outer panel 10 and the rear end of an inner panel 11 for constituting a rear pillar 3 and a back door hinge 4 is installed at upper/lower two places on the rear surface of the extension panel 12. A first reinforcement 14 and a second reinforcement 15 are arranged continuously inside the rear pillar 3 and between at least upper/lower back door hinge installation parts and a closed section is formed by these reinforcements. The first reinforcement 14 is arranged on the frontside back surface of the extension panel 12 and tightened to the back door hinges 4, 5. The extension part 15c more inside than a flange for joining of the car width direction inside of the second reinforcement 2 is held and joined between the extension panel 12 and the rear end of the inner panel 11.