The present invention provides a positioning device configured to position a glass substrate. The positioning device comprises a support base, a pair of first positioning mechanisms located on two neighboring sides of the glass substrate, a pair of second positioning mechanisms located on another two neighboring sides of the glass substrate, respectively, a pair of connecting bars, a driving member, a gear group and a conveying belt sleeved on the gear group. One end of the one of the pair of connecting bar is fixed with the conveying belt, and another end is fixed with one of the pair of first positioning mechanisms. One end of another one of the pair of connecting bar is fixed with the conveying belt, and another end is fixed with another one of the pair of first positioning mechanisms.