The 31-year-old says her close friend has a unique style and can pull of any outfit because of her classic appearance.
"The first thing that springs to mind (when thinking about Keira) is the 1940s. I think of her as glamorous in that kind of timeless movie-star way, but she can be grungy in this very cool 1990s way," Marie Claire magazine quoted Miller as saying.
"You say this about people who have style, but it is true - she genuinely doesn't think about the way she looks or how she puts herself together. She could throw on a bin bag and look beautiful," she added.
Knightley, 28, has been the face of numero