A lens barrel detachably attached to a camera body includes a fixed tube section that has a base end installed at the camera body, and a top end, a first pitch screw section being formed on an inner peripheral surface of the top end; a movable tube section that is a tube member configured to hold a plurality of lens and has a second pitch screw section on the movable tube side formed at an outer peripheral surface, and is located so as to be movable inside the fixed tube section in such a state that the second pitch screw section is threadedly engaged with the first pitch screw section, the plurality of lens including two group of lenses, a first group and a second group, held within the movable tube section. The movable tube section having a fixed diaphragm plate that is detachable.