To obtain a high-performance, inexpensive and light weight converter lens by constituting the lens so that it may be provided with at least two lens groups and also these two lens groups may be provided with a diffraction surface, respectively.

The converter lens CL is mounted on the object side of a master lens ML1 at the telephopto end, and the converter lens CL is constituted of three lenses in three groups; positive lens groups constituted of a negative meniscus lens having a convex face on the object side and a positive convex/plane lens and a negative biconcave lens. The image side face of the positive convex/ plane lens and the object side face of the negative biconcave lens are formed as the diffraction surfaces, and the image field side face of the negative biconcave lens is made aspherical. Each diffraction surface is provided with an aspherical surface work. As for the positive lens groups, chromatic aberration is not well balanced only by the aspherial surface work of the diffraction surfaces, then, in order to compensate for lack, the positive lens groups are constituted of two lenses. Besides, the 1st lens is made of glass, and the 2nd lens and the 3rd lens are made of acrylic resin.