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.