Structural member

A structural member comprising an edge portion T1 and an edge portion T2 opposing the edge portion T1 in plan view in height direction (Z axis direction);

• when an axis direction connecting the edge portion T1 and the edge portion T2 is regarded as an X axis direction, the structural member comprises an edge portion T3 located on a Y axis direction (an axis direction orthogonal to the X axis direction) side than the edge portion T2, the structural member includes, along the X axis direction, a region A including the edge portion T1, and a region B located on the edge portion T2 side than the region A and including the edge portion T2 and the edge portion T3;
• in a cross-section perpendicular to the X axis direction, the region A includes a closed cross-section portion A whose outer rim shape is one closed cross-section A;
• and
• the region B includes a closed cross-section portion B satisfying the following (i) or (ii):
• (i) in a cross-section perpendicular to the X axis direction, the closed cross-section portion B includes a closed cross-section B1 and a closed cross-section B2 those are connected via a bottom portion constituting a concave portion, and are placed apart from each other, the closed cross-section B1 extends from the edge portion T1 side to the edge portion T3 side, and the closed cross-section B2 extends from the edge portion T1 side to the edge portion T2 side, or
• (ii) in a cross-section perpendicular to the X axis direction, the closed cross-section portion B incudes an open cross-section B1 and an open cross-section B2 those are formed by dividing one closed cross-section B with a concave portion, and in the closed cross-section B, a depth of the concave portion in the Z axis direction is 50% or more with respect to a maximum length of the closed cross-section B in the Z axis direction, the open cross-section B1 extends from the edge portion T1 side to the edge portion T3 side, and the open cross-section B2 extends from the edge portion T1 side to the edge portion T2 side.