To achieve excellent workability and to reduce manufacturing cost.

A fastening fixed member 1 is provided with a threaded tubular body 3 having a female threaded portion 34 and a fastening tubular body 2 having a protuberance 24. The threaded tubular body 3 is provided with a base 32 and leg portions 33 formed with the female threaded portion 34. The base 32 and the leg portions 33 are integrally formed and are formed with a slit 35 between the respective leg portions 33. A space formed portion 36 which forms a moving space MS of the protuberance 24 is provided on the threaded tubular body 3. The moving space MS is narrower in width than the width of the protuberance 24 and is provided with a narrow-width space MS1 composing a part of the slit 35 and a wide-width space MS2 having a width more than the width of the protuberance 24. The threaded tubular body 3 is enlarged in its diameter by disposing the protuberance 24 in the narrow-width space MS1 and the enlarged diameter of the threaded tubular body 3 is released by disposing the protuberance 24 in the wide-width space MS2. The fastening tubular body 2 has a convex portion 23 substantially coming into contact with an outer peripheral surface of the threaded tubular body 3 in such a condition as to dispose the protuberance 24 in the wide-width space MS2.