PURPOSE: To provide the small-sized and lightweight zoom lens which is set with a focal position at pan focusing, has about 3 times variable power ratio, has high performance in the entire variable power region, is small in the number of lens elements and is extremely short in overall length.

CONSTITUTION: This pan focusing zoom lens consists, successively from an object side, a first lens group which has a positive refracting power, a second lens group which has a negative refracting power and moves forward and backward on the optical axis at the time of variable power, a third lens group which has a positive refracting power and is stationary, a fourth lens group which corrects the focus movement by the variable power and has a positive refracting power and satisfies the conditions (2.1<fM1-3/fM<3.6). fM1-3: the combined focal length from the first lens group to the third lens group at an intermediate focal length. fM: an intermediate focal length.