A linkage worm gear for an automatic opening/closing driving mechanism, wherein the linkage worm gear is integrally and concentrically provided with a worm gear driven portion, a gear driving portion and a cam linkage portion successively in the direction of the rotation central axis thereof; worm gear teeth fitted with a driving worm gear are provided on the whole peripheral wall of the worm gear driven portion; a reset groove, a recess, a transition portion and a boss are successively provided on the periphery of the cam linkage portion; and a plurality of driving teeth are provided on part of the peripheral wall of the gear driving portion.