PURPOSE: To provide a zoom lens constituted so that a pupil position on a screen side is brought near to a first lens surface and a compact rotation prism can be used and it is provided with high optical performance extending over a whole variable power range while such a high variable power ratio as about 20-50 times is secured by properly setting the lens constitution of the respective lens groups of a three-group zoom lens.

CONSTITUTION: The zoom lens is provided with three lens groups of the first group L1 having negative refractive power, the second group L2 having positive refractive power and the third group L3 having the positive refractive power from an enlargement side in this order. In accordance with a zooming action from a short focal distance end to a long focal distance end, the first group L1 is provided with a locus being convex on the enlargement side, either of the second group L2 and the third group L3 is provided with a locus being monotonous from a reduction side to the enlargement side and the other is provided with a locus being nonlinear from the reduction side to the enlargement side.