A butt-welded joint of steel materials, base materials of the butt-welded joint being a pair of the steel materials, with end portions of the steel materials being abutted against each other, the butt-welded joint comprising a welded portion formed to extend from surfaces of the base materials to an inner portion of the base materials and straddle the end portions, wherein the base materials have a carbon concentration of 0.1 mass% or greater and 0.35 mass% or less, the welded portion includes a melted and solidified portion and a remelted and solidified portion, the melted and solidified portion being a portion resulting from melting and solidification of the end portions of the pair of base materials, the melting being caused as a result of first heating from the surfaces, the remelted and solidified portion being a portion resulting from remelting and resolidification of the melted and solidified portion, the remelting being caused as a result of reheating of the melted and solidified portion from a surface thereof, wherein the welded portion also includes a reheated solidified portion, the reheated solidified portion being a portion formed in an inner region relative to the remelted and solidified portion and having a structure resulting from a change in a structure of the melted and solidified portion, the change being due to the reheating, the change involving no melting, and being characterised in that: a width W0 of the melted and solidified portion, a depth d0 from a surface of the welded portion to a deepest portion of the melted and solidified portion, a width W1 of the remelted and solidified portion, and a depth d1 from the surface of the welded portion to a deepest portion of the remelted and solidified portion have the following relationships. 0.46 ≤ W 1 / W 0 ≤ 1,05 0.14 d 0 ≤ d 1 ≤ 0.73 d 0 the base materials have a carbon concentration of 0.1 mass% or greater and 0.35 mass% or less, the welded portion includes a melted and solidified portion and a remelted and solidified portion, the melted and solidified portion being a portion resulting from melting and solidification of the end portions of the pair of base materials, the melting being caused as a result of first heating from the surfaces, the remelted and solidified portion being a portion resulting from remelting and resolidification of the melted and solidified portion, the remelting being caused as a result of reheating of the melted and solidified portion from a surface thereof, wherein the welded portion also includes a reheated solidified portion, the reheated solidified portion being a portion formed in an inner region relative to the remelted and solidified portion and having a structure resulting from a change in a structure of the melted and solidified portion, the change being due to the reheating, the change involving no melting, and being characterised in that: a width W0 of the melted and solidified portion, a depth d0 from a surface of the welded portion to a deepest portion of the melted and solidified portion, a width W1 of the remelted and solidified portion, and a depth d1 from the surface of the welded portion to a deepest portion of the remelted and solidified portion have the following relationships. 0.46 ≤ W 1 / W 0 ≤ 1,05 0.14 d 0 ≤ d 1 ≤ 0.73 d 0