A cam mechanism of a zoom lens which includes a front optical element and
a rear optical element positioned behind the front optical element in an
optical axis direction, the front optical element and the rear optical
element being guided linearly in the optical axis direction, the cam
mechanism including a cam ring having a first cam groove, for moving the
front optical element in the optical axis direction, and a second cam
groove, for moving the rear optical element in the optical axis
direction, both the first cam groove and the second cam groove being
formed on one of an inner peripheral surface and an outer peripheral
surface of the cam ring. The first cam groove is positioned behind the
second cam groove in the optical axis direction.