PURPOSE: To reduce the variation of bending of an image surface at the focusing time and to obtain a zoom lens having wide angle zooming of 70° or more view angle at its wide end, F/2.8 brightness and a comparatively simple constitution by changing a proper air interval in a back group converging system.

CONSTITUTION: The air interval between the front group diverging system I and the rear group converging system II by moving both the systems I , II as shown by the arrow to perform zooming. At the focusing time, the front group diverging system I is delivered to the front as shown by the arrow and a front group IIa out of the rear group converging system II is interlocked with the delivery of the system I and moved to the back to perform focusing from the infinite point to a near distance. The air interval d15 between the IIa and IIb at the focusing of an object point having 1m distance is 1.42.