A structural body formed in a plate-like shape and intended to be positioned with respect to a positioning device, the positioning device including a pair of positioning protrusions and configured to support a first surface of the structural body, the structural body comprising: a pair of positioning holes (220,221) formed through two end portions of the structural body and configured such that the pair of positioning protrusions can be inserted into the pair of positioning holes (220,221); a pair of first position detection areas (230,231) formed on a second surface of a first end portion through which a first one of the pair of positioning holes (220,221) is formed; and a pair of second position detection areas (232,233) formed on a second surface of a second end portion through which a second one of the pair of positioning holes (220,221) is formed, wherein the first one of the pair of positioning holes (220,221) is formed apart from an axis line connecting the pair of first position detection areas (230,231), the second one of the pair of the positioning holes (220,221) is formed apart from an axis line connecting the pair of second position detection areas (232,233), a pair of protruding sections (210,211) protruding outwardly are formed at the two end portions, the first one of the pair of the positioning holes (220,221) and the pair of first position detection areas (230,231) are formed at a first one of the protruding sections (210,211), and the second one of the pair of the positioning holes (220,221) and the pair of second position detection areas (232,233) are formed at a second one of the protruding sections (210,211), the second surface of the first one of the pair of protruding sections (210,211) includes a region that is surface treated by painting, attaching stickers or sanding and has a reduced specularity with respect to external light to increase a difference in luminance from the pair of first position detection areas (230,231), and the second surface of the second one of the pair of protruding sections (210,211) includes a region that is surface treated by painting, attaching stickers or sanding and has a reduced specularity with respect to external light to increase a difference in luminance from the pair of second position detection areas (232,233). a pair of positioning holes (220,221) formed through two end portions of the structural body and configured such that the pair of positioning protrusions can be inserted into the pair of positioning holes (220,221); a pair of first position detection areas (230,231) formed on a second surface of a first end portion through which a first one of the pair of positioning holes (220,221) is formed; and a pair of second position detection areas (232,233) formed on a second surface of a second end portion through which a second one of the pair of positioning holes (220,221) is formed, wherein the first one of the pair of positioning holes (220,221) is formed apart from an axis line connecting the pair of first position detection areas (230,231), the second one of the pair of the positioning holes (220,221) is formed apart from an axis line connecting the pair of second position detection areas (232,233), a pair of protruding sections (210,211) protruding outwardly are formed at the two end portions, the first one of the pair of the positioning holes (220,221) and the pair of first position detection areas (230,231) are formed at a first one of the protruding sections (210,211), and the second one of the pair of the positioning holes (220,221) and the pair of second position detection areas (232,233) are formed at a second one of the protruding sections (210,211), the second surface of the first one of the pair of protruding sections (210,211) includes a region that is surface treated by painting, attaching stickers or sanding and has a reduced specularity with respect to external light to increase a difference in luminance from the pair of first position detection areas (230,231), and the second surface of the second one of the pair of protruding sections (210,211) includes a region that is surface treated by painting, attaching stickers or sanding and has a reduced specularity with respect to external light to increase a difference in luminance from the pair of second position detection areas (232,233).