To obtain an anamorphic converter of the rear converter system which is especially most suitable for a converter for the cinema and excellent in optical performance, and in which an effective image surface of an imaging optical system can be sufficiently utilized. The anamorphic converter includes at least an anamorphic lens disposed on an image side of an imaging optical system, and in the anamorphic converter, when a focal length conversion magnification in an arbitrary cross section X containing an optical axis of the anamorphic converter is assigned x, a focal length conversion magnification in a cross section Y containing an optical axis and being perpendicular to the cross section X is assigned y, an aspect ratio of an image pickup range in an image surface of the imaging optical system is assigned AR1, and an aspect ratio of an effective area of image pickup means is assigned AR2, the following relationship is established:

0.9(AR1x)/(AR2y)1.1.