PURPOSE: To prevent a ring body from inadvertently slipping out from a push plug and make it easy to fit it to a neck of a container by protruding a boss which is capable of contacting with either the external surface of an opener body or the internal surface of the ring.

CONSTITUTION: The production method comprises closing an upper mold 1, a central mold 2 and a lower mold 3 and injecting a fused synthetic resin 5 into a cavity 4. When the synthetic resin 5 is cured, is formed a bottle opener where connection ribs 10 at four places join a ring 9 and a push plug 8 consisting of an approximately disc cap 6 and an approximately tubular body section 7. After molding, releasing the mold 1 and pushing out the push plug 8 with the pin 12 from the molds 2, 3 form a boss 13 from the remaining piece of the connection ribs 10. Thus, the push plug 8 and the ring body 9 are taken out from the mold, and the ring 9 is externally engaged in the push plug 8, whereby the production of an opener is completed.