A fastening member according to the present invention is a fastening member including a head portion and a shaft portion including a screw thread formed therein; the shaft portion includes a main body portion, and an outer peripheral portion provided radially outside the main body portion; the outer peripheral portion in the screw thread is formed of a first alloy material, and forms a portion including at least a crest portion of the screw thread; the main body portion in the screw thread is formed of a second alloy material having a tensile strength higher than that of the first alloy material, and forms a portion including a root of the screw thread; and the outer peripheral portion in the screw thread includes a thick portion where the outer peripheral portion is maximized in thickness in a circumferential direction of the shaft portion, and a thin portion where the outer peripheral portion is minimized in thickness in the circumferential direction of the shaft portion.