A lens barrel includes a stationary member; a rotary input shaft; a manual operating ring rotatably supported by the stationary member and rotated by the rotary input shaft via a gear mechanism; an optical element movable along the optical axis by rotation of the manual operating ring; a hollow-cylindrical output gear having a cylindrical inner peripheral surface in which the rotary input shaft is fitted, and an outer gear portion; a non-circular cross section portion formed on the rotary input shaft to form an accommodation space between the rotary input shaft and the cylindrical inner peripheral surface; a ball installed in the accommodation space; and a biasing device for making the orthogonal surface and the ball come into pressing contact. The non-circular cross section portion is shaped so that the rotation of the rotary input shaft is transferred to the hollow-cylindrical output gear via the ball.
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