An automobile run channel fitting device for fitting a run channel into an automobile door sash comprising a pair of robot arms 1 and 2 which act in harmony and a run channel fitting jig 3 attached to each robot arm, wherein the run channel fitting jig 3 comprises an upper roller unit 12 adapted to push the run channel to fit it into an upper sash, a rotatable lower roller 14 adapted to push the run channel to fit it into a lower sash, and a lower roller supporting means 15 adapted to support the lower roller 14 and insert the lower roller 14 into a gap formed between an inner panel and an outer panel. The lower roller supporting means 15 comprises a sliding mechanism 17, a bending section 18 and a roller supporting section 19.