Patent ID: 7782348

Claim:
An exposing device installed in an image forming apparatus main body having an image carrier, comprising: a light source that emits scanning light; a polygonal rotating mirror that scans and deflects the scanning light in a specific scanning direction; a reflection mirror that reflects the scanning light that has been scanned and deflected at plural reflection points aligned in a specific direction for the scanning light to go incident on the image carrier, the reflection mirror being spaced from the polygonal rotating mirror along an optical axis direction that is normal to the specific direction of the plural reflection points of the reflection mirror; and a unit main body in which the polygonal rotating mirror and the reflection mirror are disposed at a specific interval along the optical axis direction, wherein the unit main body includes: a pair of attachment fixing portions that are provided on almost a same line linking the plural reflection points and fixed to the apparatus main body; and an attachment supporting portion that is supported on the apparatus main body and allows free expansion of the unit main body in a plane direction including the scanning direction of the polygonal rotating mirror and along the optical axis direction on a side where the polygonal rotating mirror is installed, wherein said attachment fixing portions fix the unit main body to the apparatus main body in such a manner that at least the movements of said reflection mirror in the optical axis direction are restricted.