An image-taking lens unit has an image-taking lens system that forms an optical image of an object and an image sensor that receives the optical image in a rectangular image-sensing region and converts the optical image into an electrical signal. The image-taking lens system includes a reflective optical element that bends the optical path. Of the lens elements constituting the image-taking lens system, the most image-side lens element called the last lens element is molded of resin, and is given a non-circular outer shape fulfilling a prescribed condition.