A synchronizing mechanism comprises a main shaft which is provided with a gear groove, at least one pair of rotating shafts which penetrate through the gear groove, and a pair of gears which are arranged in the gear groove, fixed to the rotating shafts respectively and meshed with each other. The pair of gears rotate along with the relative rotation of the pair of rotating shafts, and the rotatingspeeds of the pair of rotating shafts are consistent through the mutual meshing of the gears. The invention further provides a folding display device.