PURPOSE: To obtain a lens system where various aberrations are compensated well, by satisfying prescribed conditions in the lens system which consists of two lens groups having negative the positive refractive indexes in order from the object side and changes the air interval between these groups to perform zooming.

CONSTITUTION: The two-component zoom lens system consists of the first group I having a negative refracting power and the second group II having a positive refracting power which are arranged in order from the object side, and the air interval between the first group I and the second group II is changed to perform zooming. The first group consists of the first negative meniscus lens L1 whose convex is directed to the object, the second negative meniscus lens L2 whose convex is directed to the object, and the third positive meniscus lens L3 whose convex is directed to the object, and these lenses are arranged in order from the object side. The second group II consists of the fourth double convex lens L4, the fifth positive meniscus lens whose convex is directed to the object, the sixth double concave lens L6, and the seventh double convex lens L7, and these lenses are arranged in order from the object side. One face of the first lens L1 is formed into an aspherical surface, and conditions of expressions I and IIare satisfied when refractive indexes of the first, the second, and the third lenses are denoted as N1, N2, and N3 respectively.