A lens barrel unit includes a holder configured to hold a lens, a cam cylinder including a cam groove configured to engage with the holder and define a movement of the holder in an optical axis direction, and a projection that has a part of the cam groove and projects in the optical axis direction, and a straightforward movement cylinder configured to guide a straightforward movement of the holder, the straightforward movement cylinder including a flange forming a notch. In a process from a retraction state in which the projection is located in the notch to an image pickup state in which the projection is located outside of the notch, the straightforward movement cylinder moves relative to the cam cylinder in the optical axis direction.