A hinge includes two rotatable axle units each having two hinge shafts, two synchronizing units each disposed to make synchronous rotations of the hinge shafts, two movable bracket units each having a turnable base plate, two rotary blocks non-rotatably sleeved on the hinge shafts, and two movable plates movable relative to the rotary blocks, and two guiding bracket units, each having male and female arms respectively connected with two movable plates, and a plurality of guiding connecting members interposed between the arms. Each guiding connecting member has a protrusion and a sliding groove, and is angularly movable with the rotations of the hinge shafts. Removal of the protrusion from the sliding groove of an adjacent guiding connecting member is prevented by means of engagement of an abutting portion of the protrusion with an abutted block in the groove.