A structural member comprising at least one closing plate and a hat member, the hat member including: a top portion; two first ridges located on both edges of the top portion; two flanges joined to the closing plate; two second ridges located on edges of the two flanges; and two side walls (11,12) each located between one of the two first ridges and one of the two second ridges, wherein a length of a tubular portion formed by the hat member and the closing plate as measured in a direction in which the first ridges extend is 6 or more times a larger one H of dimensions of the two side walls (11,12) as measured in a direction perpendicular to the top portion, and wherein each of the two side walls (11,12) includes a high-strength portion (11A, 12A) and low-strength portions (11B, 12B), the high-strength portions (11A,11B) of the two side walls (11,12) facing each other, each high-strength portion (11A, 12A) extending a distance not less than 2/3 times the dimension H and not more than 3 times the dimension H as measured in the direction in which the first ridges extend, the high-strength portion (11A, 12A) having a yield strength not less than 500 MPa, the low-strength portions (11B, 12B) sandwiching the high-strength portion (11A, 12A) as determined along the direction in which the first ridges extend, the low-strength portions (11B, 12B) having a yield strength of 60 to 85 % of that of the high-strength portion (12A, 12B), wherein a dimension of each of the low-strength portions (11B, 12B) as measured in the direction in which the first ridge extends is not less than 3/5 times the dimension H and not more than twice the dimension H. a top portion; two first ridges located on both edges of the top portion; two flanges joined to the closing plate; two second ridges located on edges of the two flanges; and two side walls (11,12) each located between one of the two first ridges and one of the two second ridges, wherein a length of a tubular portion formed by the hat member and the closing plate as measured in a direction in which the first ridges extend is 6 or more times a larger one H of dimensions of the two side walls (11,12) as measured in a direction perpendicular to the top portion, and wherein each of the two side walls (11,12) includes a high-strength portion (11A, 12A) and low-strength portions (11B, 12B), the high-strength portions (11A,11B) of the two side walls (11,12) facing each other, each high-strength portion (11A, 12A) extending a distance not less than 2/3 times the dimension H and not more than 3 times the dimension H as measured in the direction in which the first ridges extend, the high-strength portion (11A, 12A) having a yield strength not less than 500 MPa, the low-strength portions (11B, 12B) sandwiching the high-strength portion (11A, 12A) as determined along the direction in which the first ridges extend, the low-strength portions (11B, 12B) having a yield strength of 60 to 85 % of that of the high-strength portion (12A, 12B), wherein a dimension of each of the low-strength portions (11B, 12B) as measured in the direction in which the first ridge extends is not less than 3/5 times the dimension H and not more than twice the dimension H.