An exposure device to expose an exposure element includes a light source; an optical system to guide light emitted from the light source to the exposure element; and an optical housing, configured with a plurality of plates, to support the light source and the optical system. At least one of the plurality of plates configuring the optical housing is formed with a plurality of grooves on each of a first face and a second face with a given pitch on the one of the plurality of plates, the first face and the second face being opposite faces with each other. The plurality of grooves are arranged by shifting the center of each of grooves formed on the first face and the center of each of grooves formed on the second face.