An anamorphic converter, which can be inserted into and removed from a lens group of an image-formation optical system, includes an anamorphic lens that satisfies the following conditions 0.9<(AR1.beta.x)/(AR2.beta.y)<1.1 (AR2.sup.2+1).beta.y.sup.2/(AR1.sup.2+1)>1 wherein .beta.x represents a first focal distance magnification scale at a first cross-section containing an optical axis of the anamorphic lens, .beta.y represents a second focal distance magnification scale at a second cross-section which is perpendicular to the first cross-section and contains the optical axis, AR1 represents an aspect ratio of an image-taking range in a field of the image-formation optical system, and AR2 represents an aspect ratio at an effective range of an image-taking unit disposed at an object image side of the lens group. As such, there is provided an anamorphic converter which is small and has high optical performance, suitable for digital cinematography.