A bumper beam comprising: a closing plate; and a hat member curved along a longitudinal direction to protrude in a direction of the closing plate, wherein the hat member includes: a top plate; two first ridges each positioned on a respective one of both ends of the top plate; two flanges joined to the closing plate; two second ridges each positioned at an inner end of a respective one of the flanges; and two walls each positioned between a respective one of the first ridges and a respective one of the second ridges, characterized in that the hat member includes: a high-strength portion including a longitudinally middle portion of each of the two walls, the high-strength portion extending a length of at least 250 mm and having a tensile strength not lower than 1.5 GPa; and a low-strength portion provided in the hat member curved along the longitudinal direction to protrude in the direction of the closing plate, the low-strength portion located outward of the high-strength portion in the longitudinal direction, the low-strength portion extending a length not smaller than a height of the walls as determined along the longitudinal direction, the low-strength portion extending from one of the two second ridges through the two walls and the top plate to the other one of the two second ridges, and the low-strength portion having a tensile strength lower than a tensile strength of the longitudinally middle portions of the two walls. a closing plate; and a hat member curved along a longitudinal direction to protrude in a direction of the closing plate, wherein the hat member includes: a top plate; two first ridges each positioned on a respective one of both ends of the top plate; two flanges joined to the closing plate; two second ridges each positioned at an inner end of a respective one of the flanges; and two walls each positioned between a respective one of the first ridges and a respective one of the second ridges, characterized in that the hat member includes: a high-strength portion including a longitudinally middle portion of each of the two walls, the high-strength portion extending a length of at least 250 mm and having a tensile strength not lower than 1.5 GPa; and a low-strength portion provided in the hat member curved along the longitudinal direction to protrude in the direction of the closing plate, the low-strength portion located outward of the high-strength portion in the longitudinal direction, the low-strength portion extending a length not smaller than a height of the walls as determined along the longitudinal direction, the low-strength portion extending from one of the two second ridges through the two walls and the top plate to the other one of the two second ridges, and the low-strength portion having a tensile strength lower than a tensile strength of the longitudinally middle portions of the two walls. a top plate; two first ridges each positioned on a respective one of both ends of the top plate; two flanges joined to the closing plate; two second ridges each positioned at an inner end of a respective one of the flanges; and two walls each positioned between a respective one of the first ridges and a respective one of the second ridges, characterized in that the hat member includes: a high-strength portion including a longitudinally middle portion of each of the two walls, the high-strength portion extending a length of at least 250 mm and having a tensile strength not lower than 1.5 GPa; and a low-strength portion provided in the hat member curved along the longitudinal direction to protrude in the direction of the closing plate, the low-strength portion located outward of the high-strength portion in the longitudinal direction, the low-strength portion extending a length not smaller than a height of the walls as determined along the longitudinal direction, the low-strength portion extending from one of the two second ridges through the two walls and the top plate to the other one of the two second ridges, and the low-strength portion having a tensile strength lower than a tensile strength of the longitudinally middle portions of the two walls. a high-strength portion including a longitudinally middle portion of each of the two walls, the high-strength portion extending a length of at least 250 mm and having a tensile strength not lower than 1.5 GPa; and a low-strength portion provided in the hat member curved along the longitudinal direction to protrude in the direction of the closing plate, the low-strength portion located outward of the high-strength portion in the longitudinal direction, the low-strength portion extending a length not smaller than a height of the walls as determined along the longitudinal direction, the low-strength portion extending from one of the two second ridges through the two walls and the top plate to the other one of the two second ridges, and the low-strength portion having a tensile strength lower than a tensile strength of the longitudinally middle portions of the two walls.