The present invention provides a barrier unit, of which the blades can be opened fully.The barrier unit is designed to be attached to a camera in order to protect the lens of the camera and is ready to open or close as needed. The barrier unit includes: a base with a cylindrical portion; a first ring, which is arranged so as to rotate around the cylindrical portion; and first and second blades, which are interlocked with the first ring and which are gradually opened and closed as the first ring rotates. When one of the first and second blades is fully opened, the first ring is further movable to turn the other blade in a closing direction.