Lens barrel and optical device

A lens barrel comprising:

• barrier blades that open and close in a directional orthogonal to an optical axis of an imaging optical system;
• an optical system retention frame that includes a first surface provided in a direction orthogonal to the optical axis, the optical system retention frame retaining the optical system and being relatively movable with respect to the barrier blades in a direction along the optical axis;
• and
• a coupling plate that includes a second surface that is relatively movable with respect to the first surface, the coupling plate causing the barrier blades to open and close by the coupling plate rotating about the optical axis;
• wherein, in a state in which the barrier blades are opened, the first surface is capable of moving in the optical axis direction without abutting against the second surface and, in a state in which the barrier blades are closed, the first surface abuts against the second surface and movement of the first surface in the optical axis direction is restricted.