A lens barrel (1, 301) that has a diaphragm (2, 302) which aperture diameter can be changed, a fixed portion (3, 303) that stores the diaphragm, a diaphragm ring (4, 304) that is rotatably attached to the fixed portion (3, 303) so as to adjust an aperture diameter of the diaphragm; comprising: provided that a portion of the diaphragm ring (4, 304) facing to the fixed portion (3, 303) or a portion of the fixed portion facing to the diaphragm ring is "a first facing portion" and a portion of the fixed portion facing to the first facing portion or a portion of the diaphragm ring is "a second facing portion", - first and second projections that are located at two positions along a peripheral direction of the diaphragm so as to be energized on a side of the diaphragm ring from the diaphragm; - a fitting member (51, 351) that is formed on a side of the diaphragm ring (4, 304) such that the first and second projections (50A, 50B, 350A, 350B) are alternatively fitted thereinto according to the rotation position of the diaphragm ring (4, 304) and the diaphragm ring (4, 304) is integrally rotated with the diaphragm (2, 302), and - a link releaser (52, 352) that is configured that fitting of the first and second projections (50A, 50B, 350A, 350B) into the fitting member (51, 351) is released and the diaphragm ring (4, 304) rotates, being separated from the diaphragm (2, 302); and - a click mechanism (6, 306) that is formed or located at the first facing portion and the second facing portion so as to give a feeling of a click to rotation of the diaphragm ring (4, 304); - the click mechanism (6, 306) that has a spring member (60, 360) for clicking attached to the first facing portion, a locking member (61, 361) that is energized on a side of the second facing portion through the spring member for clicking (60, 360), and a locked member (62, 362) that is formed or located on a side of the second facing portion so as to lock the locking member (61, 361); - the second facing portion that has a locked surface (P2a) having two or more locked members (62, 362) in a peripheral direction, and - a substantially flat surface (P2b) that has no locked member (62, 362); whereby the locking member (61, 361) slides on the locked surface (P2a) when the diaphragm ring (4, 304) is rotated, fitting the first projection (50A, 350A) into the fitting member (51, 351) and the locking member (61, 361) slides on the substantially flat surface (P2b) when the diaphragm ring (4, 304) is rotated, fitting the second projection (50B, 350B) into the fitting member (51, 351). - first and second projections that are located at two positions along a peripheral direction of the diaphragm so as to be energized on a side of the diaphragm ring from the diaphragm; - a fitting member (51, 351) that is formed on a side of the diaphragm ring (4, 304) such that the first and second projections (50A, 50B, 350A, 350B) are alternatively fitted thereinto according to the rotation position of the diaphragm ring (4, 304) and the diaphragm ring (4, 304) is integrally rotated with the diaphragm (2, 302), and - a link releaser (52, 352) that is configured that fitting of the first and second projections (50A, 50B, 350A, 350B) into the fitting member (51, 351) is released and the diaphragm ring (4, 304) rotates, being separated from the diaphragm (2, 302); and - a click mechanism (6, 306) that is formed or located at the first facing portion and the second facing portion so as to give a feeling of a click to rotation of the diaphragm ring (4, 304); - the click mechanism (6, 306) that has a spring member (60, 360) for clicking attached to the first facing portion, a locking member (61, 361) that is energized on a side of the second facing portion through the spring member for clicking (60, 360), and a locked member (62, 362) that is formed or located on a side of the second facing portion so as to lock the locking member (61, 361); - the second facing portion that has a locked surface (P2a) having two or more locked members (62, 362) in a peripheral direction, and - a substantially flat surface (P2b) that has no locked member (62, 362); whereby the locking member (61, 361) slides on the locked surface (P2a) when the diaphragm ring (4, 304) is rotated, fitting the first projection (50A, 350A) into the fitting member (51, 351) and the locking member (61, 361) slides on the substantially flat surface (P2b) when the diaphragm ring (4, 304) is rotated, fitting the second projection (50B, 350B) into the fitting member (51, 351).