PURPOSE: To realize such an internal focusing zooming that focusing is executed by the second and succeeding follower lens groups, and to shorten a focusing time at an AF focusing time by simple components without deteriorating the operability of one-operation zooming.

CONSTITUTION: An engagement pin 16 integrally provided on the second and succeeding-group lens holding rings 4 participating in both of the zooming and the focusing is inserted in a cam groove both for zooming and focusing 2a provided on a cam ring 2 and a straight advance groove 7c provided on a focus interlocking ring 7. By the rotation of a focusing operation ring 8 provided on a zooming operation ring 9, the ring 4 participating in both of the zooming and the focusing is moved in an optical axis direction and the focusing is executed. Then, the one-operation and internal focusing zoom is realized.