Optical scanning apparatus having an air path for airflow generated by a rotating mirror

At least one exemplary embodiment is directed to a first airflow guide device covering an upper portion of a polygon mirror and having respective opening portions in an upper surface and a lower surface. The lower surface opening portion can have an annular wall opened in the direction all around the perimeter of the polygon mirror, facilitating an airflow path capable of circulating an airflow between the upper surface opening portion and the lower surface opening portion. Thus, airflow generated in a vertical direction in association with the rotation of the polygon motor, is guided, and variations in pressure applied to the polygon motor are reduced, thus facilitating an increase in the rotation accuracy of the polygon motor.