Abstract: A zoom lens of this invention comprises in successive order from the object side a first group having a positive refractive power and fixed, a second group having a negative refracting power for effecting a variation of image magnification by moving on the optical axis, a third group having a positive power for effecting a light condensing action and fixed, and a fourth group moving on the optical axis so as to keep an image surface position to be changed in response to a move of the second group and a move of the object in a constant positional relation with the reference surface. Comparatively large air space is provided between the third and fourth groups of the zoom lens.