An optical scanner for an image forming apparatus of the present invention
includes a polygonal mirror for steering a scanning beam incident thereto
and an optical device located in the vicinity of the polygonal mirror. The
polygonal mirror and optical device are supported by a housing. A heat
radiation guide adjoins the polygonal mirror and is formed integrally with
or separately from the housing. The heat radiation guide has a guide
surface inclined relative to the axis of rotation of the polygonal mirror
and intersecting a plane virtually formed by a scanning beam.
