PURPOSE: To provide an inexpensive image forming device light in weight, high in rigidity, excellent in slidability on other members, good in electromagnetic wave shielding property and sure in continuity.

CONSTITUTION: This structural body is provided with a housing 1 having a pair of side plates 2 and 3 and a bottom plate 4 supporting the side plates 2 and 3, and an optical bottom plate 15 arranged at the upper part of the housing 1 and supporting an optical system. At least the side plates 2 and 3, the bottom plate 4 and the optical bottom plate 15 are formed of a lubricated steel plate, the lubricant applying amount of the lubricated steel plate is 700-1100mg/m2, and a surface resistance value is ≤500mΩ.