A turnbuckle (10) is made by a method including preparing an iron tube (40) having a longitudinal through-hole (42). A diameter of each of two ends (50) of the iron tube (40) is reduced to form a coupling section (12) having an engaging hole (121), with an interconnecting section (11) interconnected between the coupling sections (12). The interconnecting section (11) is punched in a direction perpendicular to the longitudinal through-hole (12) to form a transverse through-hole (13) perpendicular to the longitudinal through-hole (42) and between the coupling sections (12), leaving two opposite peripheral wall portions (44) spaced by the transverse through-hole (13) and forming a bend (14) extending inward from each of two end edges (46) of each peripheral wall portion (44) into the longitudinal through-hole (42), An abutting portion (15) is formed between each bend (14) and one of the end edges (46) of one of the peripheral wall portions (44). Inner threading is formed in the engaging hole (121) of each coupling section (12).