PURPOSE: To attain a higher variable power and higher zoom ratio by constituting a zoom converter in such a manner that the converter has at least three groups and that variable magnification is executed by moving at least the two groups thereof along the optical axis.

CONSTITUTION: This zoom converter consists, successively from an object side, the first group Gr1 and the second group Gr2 and is negative and positive. The zoom converter composed of the positive, negative and positive three groups which are capable of executing the variable magnification by moving toward the front of a master lens M1 (the third group Gr3). The first group Gr1 consists of a negative meniscus lens concave a negative lens of biconcave and biconvex positive lens to an image side and second group Gr2 consists of a positive meniscus lens convex to the object side, a negative meniscus lens concave to the image side, a positive meniscus lens convex to the object side, a negative meniscus lens concave to the image side, a biconvex positive lens and a luminous flux regulating plate. The master lens M1 (the third group Gr3) consists of a convex to the object side, a biconcave negative lens and a combined lens of a biconvex positive lens and a negative lens concave to the object side.