Abstract: A vehicle door mounting system mounts a door on a vehicle body by bringing a hinge member on the door into engagement with a hinge member on the vehicle body and inserting a hinge pin into hinge pin holes of the hinge members. The mounting system has a robot, and a door holding jig and a hinge pin inserting jig which are mounted on the robot. The robot is arranged so that it brings the door to a predetermined position with respect to the vehicle body where the hinge member on the door is engaged with the hinge member on the vehicle body while the door holding jig holds the door. The hinge pin inserting jig is separable from the door holding jig and is moved between an operative position where it inserts the hinge pin into the hinge pin holes and a hinge pin setting position where the hinge pin is set to the hinge pin inserting jig.