<p>Disclosed is a structure which comprises structural members (1) that form a frame shape having four sides and closed-sectional structural members (4) serving as reinforcing materials disposed at corners (2) where the structural members (1) intersect with each other. The closed-sectional structural members (4) each include two lateral portions (5) that are disposed so as to be remote from each other in the thickness direction of the structural members (1) and that extend in directions parallel to the surfaces of the structural members (1) and two longitudinal portions (6) each connecting first ends of the two lateral portions (5) and second ends of the two lateral portions (5). The closed-sectional structural members (4) each have a first opening (7) facing the inner circumferential flat surfaces (1a) of the structural members (1) and a second opening (8) facing the inside of the structural members (1). The height ho of the closed-sectional structural members (4) is substantially the same as the thickness H of the structural members (1), and all the edges of the first openings (7) are joined to the inner circumferential flat surfaces (1a) of the structural members (1). The flattening serving as a ratio of the maximum width H of the second openings (8) to the height ho of the closed-sectional structural members (4) is set to be larger than 1.0 and smaller than or equal to 3.0.</p>
