Lens barrel

A collapsible lens barrel, comprising:

• an opening/closing unit that includes an opening/closing portion openable and closable along a plane orthogonal to an optical axis to control a light amount, and a maintaining portion that maintains an opened state of the opening/closing portion;
• an inner lens disposed closer to an object than the opening/closing unit is, the inner lens being orthogonal to the optical axis;
• an inner frame that holds the inner lens;
• an outer lens disposed closer to the object than the inner lens is, the outer lens being orthogonal to the optical axis;
• an outer frame that holds the outer lens;
• and
• a restriction portion that restricts operation of the maintaining portion by restriction applied from the outer frame to the maintaining portion via the 15 inner frame to maintain the opened state of the opening/closing portion when the outer frame and the inner frame are collapsed.