A lens cap unit includes a mounting part mounted on a fixed cylinder in which a movable lens cylinder is movably contained, at least one barrier provided on the mounting part to be movable between a closed position covering a leading end portion of the movable lens cylinder and an opened position opening the leading end portion of the movable lens cylinder, and a cam protrusion provided on the barrier. The cam protrusion engages with the movable lens cylinder at a position outside an effective diameter of the movable lens cylinder.