Provided is a novel screw fastening structure with a locking function. The screw fastening structure includes a first screw element 11 and a second screw element 12 which is screwed and fastened to the first screw element 11. One of the first and second screw elements has an engagement recessed part R which is opened toward the other side, and the other screw element has an engagement projecting part P which is inserted in the engagement recessed part R in a fastened state. The engagement recessed part R has an inner circumferential surface extending straight along the axial direction so as to have a cylindrical shape. The engagement projecting part P is formed in a columnar shape or a cylindrical shape so as to have a maximum-diameter section at one location in the axial direction. The maximum-diameter section of the engagement projecting part P and the inner circumferential surface of the engagement recessed part R are eccentric relative to each other so as to be in pressure contact with each other only at portions thereof in the circumferential direction in the fastened state. The maximum-diameter section of the engagement projecting part P is located at a predetermined distance from the proximal end of the engagement projecting part P such that the engagement projecting part P can advance and retreat in the axial direction with respect to the engagement recessed part R in a state where the maximum-diameter section is in pressure contact with the inner circumferential surface of the engagement recessed part R only at the portions in the circumferential direction.L'invention concerne une nouvelle structure de fixation par vis avec une fonction de verrouillage. La structure de fixation par vis comprend un premier élément de vis 11 et un deuxième élément de vis 12 qui est vissé et fixé au premier élément de vis 11. L'un des premier et deuxième éléments de vis a une partie d'engagement en creux R qui est ouverte vers l'autre côté, et l'autre élément de vis a une part
