Sealability between a cover member and a transparent member of an optical scanning apparatus is improved to improve dustproof performance. An optical scanning apparatus includes an elastic member 75 for sealing a portion between a cover member 70 and a glass member 90, the elastic member 75 being formed on the cover member 70 so as to surround an opening portion 42, the elastic member 75 being formed from a material that differs from that of the cover member 70. The elastic member 75 has a protrusion 75a that extends towards the glass member 90. The protrusion 75a fills a gap between the cover member 70 and the glass member 90 by contacting the glass member 90 and being elastically deformed.