An automatic return device for glass doors includes a hydraulic hinge assembly having a first base, a piston unit, a first drive axle and a first grip unit and a leaf positioning assembly having a second base, a slide seat unit, a second drive axle, and second grip unit. The first and second bases are connected to a doorframe. The piston unit and first drive axle are set in the first base. The first drive axle interacts with the piston unit to generate oil pressure. The first and second drive axles are connected to the first and second grip units that grip a glass door. The slide seat unit and the second drive axle are set in the second base. When the second drive axle pivots, the slide seat unit positions the second drive axle at a predetermined pivotal angle.