The present invention provides a butt-welded joint of a welded structure, including: a pair of target metals; a weld bead formed by irradiating a first high-energy density beam to a butt portion between the pair of the target metals, the weld bead having a width W on an irradiated side surface; and a pair of altered zones formed, on a surface of the butt-welded joint having the first high-energy density beam irradiated thereto, by irradiating a second high-energy density beam to the surface, the pair of the altered zones having a band shape extending in parallel to the weld bead, and the pair of the altered zones consisting of a pair of heat-affected portions and molten and solidified metals located on a right side and a left side relative to the center of the weld bead in the width direction.