A lens barrel and an optical device that can be reduced in size while maintaining high optical performance. A lens barrel has a cam ring (3) that is disposed for rotation about an optical axis. A linked member (37) can advance and recede in a direction of the optical axis with rotation of the cam ring about the optical axis. First and second cam grooves (3d, 3e) is formed in the cam ring for guiding advancement and receding of the linked member in the direction of the optical axis. First and second cam-followers (8a, 8b) are provided in the linked member and are engageable with the first cam groove and the second cam groove, respectively. The second cam-follower is disengageable from its corresponding second cam groove. A depth of the second cam groove in a position where the second cam-follower is introduced into the second cam groove is deeper that of the second cam groove at a different position.