To provide a high tensile bolt used in a civil engineering structure and the like having a function for preventing the scattering caused by the breaking by delayed fracture during the use.

This high tensile bolt has a material having elongation higher than that of a high tensile bolt material, and having a cross-sectional area gradually increased from the neighborhood of the end part to the end part at both end parts, in the internal axial direction of the high tensile bolt, or both end parts of the high tensile bolt are composed of fixing parts made out of the material having elongation higher than that of the high tensile bolt material. The material 2 having elongation higher than that of the high tensile bolt material has breaking elongation of 15 % or more, preferably about 20 %, toughness represented by Charpy absorption energy at 0°C of 27J or more, preferably 47J or more, and a yield rate of 80 % or less in a case of a metallic material, and has breaking elongation of about 20 % to prevent over elongation in breaking, and high toughness in a case of a viscoelastic material, and further a sensor for detecting the distortion in the material is axially continuously mounted according to the necessity.