A converter unit for a lens unit of a camera, which is able to match optical axes of a plurality of kinds of converter lenses with different magnifications, which are revolvably mounted on a rod, with an optical axis of the lens unit properly. One of the converter lenses is revolvably mounted on the rod by two bearings through a connecting member. One of the bearings is attached on an eccentric external circumference of a collar member attached on the rod. The rotation of the collar member adjusts an eccentric direction of the collar member and the direction of an optical axis of the converter lens.