Lens barrel and optical device

The present invention provides a miniaturized lens barrel and optical instrument. The lens barrel (1) is constituted to be provided with a lens (L2) which is retained in a retaining frame (82) pivotally supported by a shaft portion (83) parallel to the optical axis (A), and which moves between a first position and a second position in a plane perpendicular to the optical axis by rotation of the retaining frame about the shaft portion; a protuberance (85) formed to protrude in a direction perpendicular to the optical axis; and a moving member (70) which is moveable with respect to the retaining frame and which includes a retaining face portion (70a) which, in a state where it abuts the protuberance, retains the lens in the first position, and a recessed portion (72) formed at one portion of the retaining face portion; and is constituted such that the protuberance moves between a state where it abuts the retaining face portion, and a state where it is accommodated in the recessed portion, in accordance with movement of the moving member, and the lens is retained in a second position in the state where the protuberance is accommodated in the recessed portion.