A buckle structure has a female part and a male part. The female part has a cavity for insertion of an axial tab formation of the male part, which has transverse seats on opposite lateral edges for engagement by fastening members on the female part. The fastening members have teeth located on opposite sides of a longitudinal direction of coupling of the buckle, which form between them a transverse aperture for the insertion of the tab formation. The buckle has button-like release members connected to the fastening members and operable manually by pressing transverse to the buckle, to disengage the fastening members from the seats. The fastening members and the release members act in coinciding or parallel transverse directions, so that the simultaneous pressing of the buttons towards each other causes the fastening teeth to move away from the engagement seats on the tab formation.