Diaphragm device and lens barrel

A diaphragm device that changes a diameter of an aperture stop, comprising:

• a bottom plate that is formed in an annular shape on which an aperture for an optical path is formed;
• a plurality of diaphragm blades that are arranged around an optical axis of the optical path and attached to the bottom plate in a rotatable manner;
• a blade rotation member that is formed in an annular shape and is rotated relative to the bottom plate in a circumferential direction around the optical axis to rotate the diaphragm blades with respect to the bottom plate;
• and
• biasing members that bias the respective diaphragm blades to one side in a rotation direction of the multiple diaphragm blades with respect to the bottom plate, wherein
• either one of the set of the diaphragm blades and the blade rotation member has cam grooves that cause the diaphragm blades to rotate with respect to the bottom plate to change the diameter of the aperture stop,
• either the other of the set of the diaphragm blades and the blade rotation member has cam protrusions that are formed thereon or fixed thereto and are engaged with the cam grooves,
• the diaphragm blades have biasing protrusions that are formed thereon or fixed thereto, protrude from surfaces thereof, and are engaged with the biasing members, and
• the cam protrusions are in contact with side surfaces of the cam grooves by biasing force of the biasing members.