In the present invention, an edge face of an diaphragm ring (4) has a part (a locked portion) wherein a plurality of depressions (62) are formed and a substantially flat surface portion wherein no depression (62) is formed, and by a simple operation of operating a link releaser (52) so as to rotate the diaphragm ring (4), it is possible to switch between a click mode and a non-click mode. When taking still images, a diaphragm value can be fixed by using the click mode, and when video is taken, the diaphragm value can be smoothly changed during imaging by using the non-click mode.