The present invention discloses a method and machine for automatically fabricating zippers. The method comprises steps: parallel placing two tapes on the machine, injection-molding a plurality of plastic teeth on two opposite edges of the tapes, leaving untoothed blank regions on the tapes periodically, and applying plastic films onto the tapes; transporting the filmed tapes to a punching device to punch a positioning hole on each blank region; inserting each section of the plastic teeth, which is between two adjacent blank regions, into at least one slider, and using the positioning holes as reference points to injection-mold a plurality of bayonets on the blank regions respectively, wherein each positioning hole corresponds to a set of bayonets; and cutting off the tapes at the blank regions to obtain a plurality of zippers.