Abstract: The invention relates to an automatic locking slider for a slide fastener, wherein: in the automatic locking slider, an auxiliary support groove 2b is further formed adjacent to a support groove 2a on a bottom side of a locking lever accommodation groove 2 on which a locking lever 3 is mounted, and an auxiliary support protrusion 3f is further formed on the inner side of a support protrusion 3a formed at the rear part of the locking lever 3; a top surface 3d is formed on an upper end of the support protrusion 3a such that a downwardly-curved part 5a formed at the back of a cover 5 contacts a top surface of the support protrusion of the locking lever, whereby the locking lever can be stably supported in the support groove of the accommodation groove.