A hinge includes two rotatable axle units disposed on a base seat and each having two rotatable hinge shafts, two movable bracket units each including a base plate, two rotary blocks non-rotatably sleeved on the hinge shafts, and two movable plates movable relative to the rotary blocks, and two synchronizing units for making synchronous rotations of the hinge shafts. Each synchronizing unit includes a first gear member having two end surfaces in form of bevel gears, and two second gear members each meshing with the respective end surface and fitted to the respective rotary block. Rotations of the hinge shafts at one side of the base seat result in rotations of the rotary blocks and the second gear members, and bring in rotations of the second gear members, the rotary blocks and the hinge shafts at the other side to make the synchronous rotations.