Provided are a reference scale and dimension measurement system that make it possible to maintain accurate measurement even if the reference scale is not disposed or projected on a measurement surface. A dimension measurement device according to the present invention is provided with: a reference scale extraction means for extracting, from photographed image data including a reference scale that includes a film that has a pattern for displaying a length reference formed on the surface thereof and a lens that is in contact with the film, an image in which an image of the length reference is formed on the basis of the relationship between a pattern function expressing the length reference projected onto the lens according to variation in a prescribed angle between the reference scale and the optical axis of a photography device and an image formation color function indicating the image of the length reference formed on the imaging device; an object of measurement extraction means for extracting an object of measurement image from photographed image data including the reference scale; and a dimension calculation means for calculating a dimension of the object of measurement on the basis of a dimension of the image in which the image of the length reference is formed and the image of the object of measurement.