A fastening member includes a first alloy portion and a second alloy portion. The first alloy portion is made of an aluminum alloy including 0.005 wt % to 5.0 wt % zinc and 0.6 wt % to 2.0 wt % magnesium and is provided to a part that comes into contact with at least one of a plurality of members serving as a fastening target. The second alloy portion is made of an aluminum alloy including more than 2.0 wt % and 5.0 wt % or less magnesium and more than 5.0 wt % and 10 wt % or less zinc and is joined to the first alloy portion.